# 125 gallon planted discus tank



## M Allred (Jan 13, 2017)

Hey Arc,
I ran a very successful 130 gallon planted Discus tank for many years.
Fluorite substrate, 96 watt compact fluorescent, CO2 injection, UV sterilizer, etc.
I wouldn't do less than 50% water changes, and a gravel vac every third day. 
That would rule out dirt. 
That was also 1 1/2 to 2 hours work each time.
I won a bunch of awards with my tank and fish pictures, which was rewarding!  
I actually ending up winning a bunch of Bing Seto's Cobalt Reds! 
That required another tank (bare bottom). 
After several years I got burned out on all that work, so water changes slacked off a little. 
As you can probably guess, fish health went downhill! 
I had kept fish since I was 15, but had had enough. 
Sold all my tanks and remaining Discus, and didn't get back into it for another 6 years. 

Presently I am running a heavily planted 65 and a 125 stocked with mostly Angelfish, Bristlenos and some Tetras, 
sumped tanks with continuous WCs. 
Pretty low upkeep, so I am enjoying the hobby much more. 
I am pretty sure I could not keep a herd of Discus thriving doing what I am doing now.
IMO your fish probably won't thrive in a dirted aquarium.


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## arcXIV (Jan 15, 2017)

Hello, thank you for your reply! So even capping the soil/flourite substrate with pool filter sand wouldn't be a good idea? I'm definitely OK with the maintenance of the 125, currently I run 4 different tanks and I will be downsizing once the 125 is up and running. I plan on it being my only tank once everyone is settled in lol. Why wouldn't they thrive in it?


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## discuspaul (Jul 27, 2010)

One of the secrets for keeping discus healthy & thriving is to keep things as simple as possible, optimize your capacity to keep the tank as squeaky clean as possible, and maintain high water quality & conditions by doing frequent, large water changes.
So M Allred's last paragraph in post #2 above is right on the money.

You'd be well advised to start off low tech with discus, at least in the early months as you gain knowledge of discus traits & behaviors, and as they grow out to maturity - so avoid the use of CO2, and keep just hardy plants which can handle the higher discus temps and grow well in pool filter sand alone (using root tab ferts) - which can easily be kept clean & harbors a minimum of undesirable bacteria.
I'd be happy to help you out with any other information you need, along with a list of plants which do well in PFS - just ask.
And btw, reduce your temp to 82 F.

Bump: Oh, and be sure to get your discus from a known reputable, reliable source for supplying good quality fish, and get them of a decent size, say min. 3", but preferably larger, to avoid stunting as much as possible. I can help you with that too.


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## arcXIV (Jan 15, 2017)

Thanks for the reply! I am by no means an expert in keeping discus, so any advice is welcome. However I feel I've got a decent handle on the basics. My discus are all sub adults at this point (at least 4+ inches, some are over 5.5) and I've grown them out over the past year in a barebottom 55 gallon. I did daily WC's for the first 6 months or so, and have gone to every other day lately and they have grown wonderfully. I order all my discus from Maryland through discus Hans, as I would not trust LFS discus even if they carried them (they don't).

My question is about soil, however. I would be capping it with pool filter sand and would just like to know what kind of soil (organic potting mix, miracle grow, ect) won't alter my water parameters. Ideally I would do maybe 1" of soil capped with 1" of sand to avoid the formation of anerobic pockets in the substrate. I have read about plenty of people moving their discus to a larger planted tank after growing them out, and this was kinda the idea all along for me lol. So why wouldn't soil be OK? And what kind could I use?


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## discuspaul (Jul 27, 2010)

M Allred, with discus experience, said: ..."your fish (discus) probably won't thrive in a dirted aquarium", and I fully agree with that, and did said so, and gave a reason why. ('thrive' being a key word)

Any type of soil used as substrate in a discus tank, even if capped with sand, will very likely accumulate & harbor all types of bacteria, both good & bad. And it's the latter which may potentially expose discus to some form of toxicity, or minimally, undesirable/unhealthy elements. Why run the risk ? - Simply go with nothing more than PFS - take this advice from someone with over 35 years' experience keeping discus, and who has experienced, or seen, most if not all of the pitfalls which can expose discus to unhealthy conditions.


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## arcXIV (Jan 15, 2017)

OK then, soil is a bad option. Perhaps I got some bad advice from a few folks at simplydiscus who have claimed to have done it with no issues. 
I guess I just don't understand the difference between having a 2" bed of sand versus a 1" bed of soil with 1" of sand on top of it. Anaerobic bacteria cannot develop and grow in substrate that is less than 4" deep at least, as they require an environment with virtually zero oxygen. So I'm confused as to what other types of bad bacteria can develop in soil that can't develop in any other substrate, such as sand, or even gravel (which allred also stated that he maintained successfully for many many years to the point where he won awards).
I'm not trying to argue, just trying to better my understanding of how to keep my fish healthy, cause really that's what it's all about anyway.
This was my previous thought process on soil capped with sand - 
any feces or uneaten food will rest on the surface of the sand bed, not break down through the cracks as with gravel, leaving it easier to clean up with a daily vacuuming. Of course, some will always break down into the sand bed, which is why it is necessary to stir it up every once in a while. From there, anything that gets down into the soil will actually help fertilize it and be processed into nutrients by the plant roots, therefore being beneficial to the health of the entire tank, as well as the fish.

Again, I'm not looking to start an argument, and if I am wrong with how any of that works, by all means, please tell me. I'm a marine biology major, so I'm somewhat skeptical when someone online tells me about "all sorts of good/bad bacteria", but then doesn't specify exactly what kinds they're referring to. The biggest problem with this hobby and the internet is people repeating things they have read someone else say before somewhere without any information or experience to back it up... And I am by no means implying that that's what you guys are saying, I'm just stating my frustrations. If my view on how this works, I'd rather find out now than down the road when the tank is already running. You're the ones with years and years of experience, so that's why I'm asking on these forums and not just doing it blindly.

So if I'm not doing soil, would it be feasible to use just straight flourite sand underneath the pool filter sand to get the same results I am looking for?


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## M Allred (Jan 13, 2017)

"I guess I just don't understand the difference between having a 2" bed of sand versus a 1" bed of soil with 1" of sand on top of it. Anaerobic bacteria cannot develop and grow in substrate that is less than 4" deep at least, as they require an environment with virtually zero oxygen. So I'm confused as to what other types of bad bacteria can develop in soil that can't develop in any other substrate, such as sand, or even gravel (which allred also stated that he maintained successfully for many many years to the point where he won awards)."

I don't know if I buy the 4" thing, I had a horrible bacterial outbreak in my 125 2 years ago, and lost 6 or so prized Angelfish, due to pulling an Amazon Swordplant. Anaerobic or not, it was swift and toxic. I was using EcoComplete and you can't vacuum that, just top of substrate stuff. After that humbling experience, I replaced the Eco with a substrate I can THORUGHLY vacuum.

I also don't buy into the notion "Malaysian Trumpet Snails keep your substrate
aerated". I highly doubt they move much more than just under the surface. I sadly have a ton of them (yeah, I know, I probably should feed less  ).
I stated I vacuumed my substrate every 3 days, That was a THOROUGH vacuuming! 
I wouldn't obsess on soil. You can grow pretty much anything you want in gravel or pool sand with a few root pellets and liquid ferts. The plants will take a little longer to get well established, that's all.

I can assure you neither Paul or myself are "internet parrots". Our records speak for themselves.
Just my opinion.


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## discuspaul (Jul 27, 2010)

My discus-keeping experience doesn't include much knowledge of bacteriology and the development of pathogens in certain mediums, but all I can tell you is that quartz-based silica pool filter sand is inert, and that any type of soil is not, and therefore who knows what elements can grow and thrive in it, anaerobic or not.

In my experience, the best, safest way to keep discus is to do so with large, frequent water changes, in either a bare bottom tank, or with nothing other than inert pool filter sand substrate in a planted environment.

I'll close this off by simply giving you one small example of what most soils can, and generally do, produce normally - and that is nitrates. And unless large, frequent (probably daily) water changes are maintained, nitrate production & maintenance of over 10 ppms, to 20 ppms or more, is readily achieved and maintained in a tank with soil substrate.
This condition may well prove to be the onset of stress with discus, which do not tolerate chronic nitrate levels at or above that measure without serious discomfort, which can of course develop into failing/ill health as a result.

But hey, go ahead & do what you think is acceptable to you to maintain these expensive fish in good health. I've tried many times over the years to achieve this in planted setups with various types of substrate, with some very disappointing results, and now I believe I know what not to do. 
That's my .02 cents.


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## klibs (May 1, 2014)

I am certainly not a discus guy but I would advise listening to the experts on this one... 'discus people' like paul and Allred have put in the time and effort (a LOT of time and effort) to be experts at raising those fish and usually when people deviate from that kind of advice bad things happen. from what I have read the gist is that the discus should always come first and if you can pull off some nice plants that's a bonus. by focusing on growing your plants first you are already likely making a mistake

personally, if I ever did discus I would not even attempt plants until I had ample experience with the fish. like the experts say, use a bit of something inert that is easy to clean or go bare-bottom. this is why discus tanks are usually very open - you need to be able to vacuum everything. personally I would want my discus to THRIVE and look beautiful as priority #1 and not be so concerned about the rest of the setup - especially in the first go-around

also, if you have never done a dirt-style setup... put a little dirt in a cup, cap with your sand, fill with water, do your water changes as you plan to do, then after a month of that check out how awful the gases that come out of that stuff smell. hard to believe it is anything but toxic... not something I would want with discus in the mix


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## discuspaul (Jul 27, 2010)

Many thanks for your appropriate comments, Klibs - your remarks and suggested approach to discus-keeping are right on, and well stated.


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## arcXIV (Jan 15, 2017)

Again, thank you for your replies everyone. This is an idea I've been kicking around in my head for a while, but I just couldn't find much information on it to make a decision. I have a pretty scientific mind I guess, and I was just looking for information to make a decision. I've decided not to do soil. As I stated in one of my earlier posts, I am by no means an expert in keeping discus, but I have a handle on how to care for them. My whole motivation for wanting to use soil was for the natural recycling of fish waste into the tanks ecosystem, therefore benefitting the health of the discus more than anything. 

I do appreciate some of the examples you guys have provided after the first couple posts, so thank you. Actual proof and examples of things going wrong is what I was looking for, not just "I've got experience, don't do that". Anyone can say that while they're regurgitating something they read somewhere else, without any first-hand knowledge of what they're saying.

You all may be well known on this forum as discus superstars or something, but I just joined it 2 days ago. Honestly, I don't particularly care what's someone's online social status is as long as they can provide details and experiences behind what they're saying. Forgive me, but I've always had a scientific mind (hence my chosen profession) and I don't always respond well when people make statements without anything backing it up. 

But hey, once we got passed all that and into the nitty gritty, you guys were helpful, so thanks


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## diverjoe (Oct 21, 2016)

M Allred said:


> Hey Arc,
> 
> I ran a very successful 130 gallon planted Discus tank for many years.
> 
> ...




Hi I have returned to the hobby after raising a family and wanted to do something less adventuresome. . I had tremendous (for me) success 3 decades ago with heavily planted 55g ug filter reverse flow and some kind of plant food by tetra and 30% weekly changes. 

I setup a 75 about 2 mos ago bdbs substrate ug filter fed flow 3gal + canister filter heavy plant community tank. Automated daily. 8-10% rodi wc and feeding pps pro daily. 7x/wk. I am new to automation pps ei and all that has changed over the years and have been studying hard daily to catch up. I have only found s couple of advocates of daily wc and am immensely interested in your experiences pearls off wisdom etc. the tank started at 8 ph TDS 250 ppm gh & oh was at top of chart. It is now averaging 7.25. Temp 77 TDS ~65 using 5 rodi water in daily changes gh 4 kh 3. I am currently working to ease TDS up to around 105. I am looking to see if I can use a TDS set point to control dosing and gain some semblance of equilibrium. I have a very eclectic mix of community parishioners everyone seems happy several spawns from multiple species and no deaths of anything in over a month including a dozen neons! Would like to eventually add a couple discus although I have never raised them before. 


Am I barking up the wrong tree? Did I give enough info?


Anything at all would be greatly appreciated! Oh and my goals are to keep 2-3 discus as centerpieces along with a mix of peaceful community fishes without being a slave to the tank and automating as much as possible so I can just sit and look at them in my free time. 


Sent from my iPhone using Tapatalk


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## discuspaul (Jul 27, 2010)

Contrary to the relative ease of keeping most species of tropicals, discus-keeping is quite another matter, and one of the first essentials is to do your homework to ensure you've got a good handle on how to keep them healthy & thriving. Otherwise you face serious disappointment by quickly losing these beautiful, but expensive fish.

Suggest you start by having a thorough read through my Beginner's Guide to Getting Started with Discus, located here in the 'FISH' section.
Just click on the first thread, the only Sticky - FAQ & Articles & you'll find it.
Discus are not difficult to keep, but require extra-ordinary treatment in the form of frequent, large fresh water changes and a regular solid tank cleansing routine, among other things. 

Novices to discus are advised not to start off with keeping them in a heavily planted environment with other tank-mates, until they become familiar with their traits, behaviors, and everyday needs. Smaller young immature fish in particular, should be grown out in a bare-bottom tank to near adult stage to avoid stunting, and one should keep no less than 5 discus together to avoid the development of potentially serious pecking order issues (bullying).
Please do some research so that you give yourself a chance to be successful keeping discus. Once you have, I'll be glad to help you out further with any additional questions you may have.
Best of luck to you.


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## discuspaul (Jul 27, 2010)

Here's a very abbreviated guide to get you started:


D-I-S-C-U-S - 6 CARDINAL RULES FOR NEWBIES TO FOLLOW


First I'd just like to mention once again that discus are hardier than many people think, and are not difficult to keep, so long as one is prepared to accept and adhere to a few key practices that will provide the best chances of success with discus.

This listing is recorded more or less in order of importance:

1) - D - Do your homework well before delving into discus. Read and research all you can beforehand. Googling will certainly help, as well as spending a good deal of time reading the posts and threads on the simplydiscus.com forum, particularly the stickies in the 'Discus Basics for Beginners' section, which will provide you with much of the material you need to digest.

2) - I - Investigate and learn of the best sources to get your discus stock. Find those breeders &/or importers that are long time, well-experienced, responsible, reputable, and known to supply high quality, healthy, and well-shaped discus. Buy your discus from one of these sources in order to insure that you get off on the best footing possible.
This is the single, most important factor in succeeding with discus.
The simplydiscus.com forum has a sponsors section which lists a good number of high quality discus suppliers in North America. Check it out.

3) - S - Set up and plan to follow a strict regular routine of fresh water changes, tank wipe-downs and cleansing, vacuuming of wastes, and regular filter and media cleaning, changes, replacements, and maintenance. Be fully prepared for the kind of commitment it takes to produce and maintain the highest water quality and conditions that you can.

4) - C - Carefully consider the type of tank set up you start with. Make sure the tank size is ample enough to start with 5 or 6 discus. Don't be tempted to begin with a tank of less than 55 or 60 gallons, and don't try to justify going smaller by just getting 1, 2, 3, or 4 discus for cost or other reasons.
Wait till you have sufficient resources to get a proper-sized tank, and the suitable size and number of fish to insure continuing good health and harmonious discus sociability.
Do not start with small, undersized, very juvenile fish which have not yet developed a more mature immune system, are more demanding to raise properly, and much more prone to health problems and other issues. Get fish of at least 3.0" in size, preferably larger.

5) - U - Undertake to start off with a bare bottom tank, unless you're getting fully adult fish and have previous good experience with fish-keeping generally, and maintaining a planted tank in particular. If you must have some decor, limit yourself to a very thin sand substrate layer, and perhaps a piece of driftwood with just a couple of small plants attached, or one or two potted plants.
Once you gain several months' of experience getting to know your discus' traits & behavior, and your discus get larger, then you may proceed to an aqua-scaped environment, to possibly include some other species of compatible discus tank-mates. Feed a varied diet, several times a day, and learn which foods will achieve a nutritious diet, by researching.

6) - S - Simplify. Keep things as simple as you can to start. Don't complicate your start with discus, at least at first, by placing them in a heavily planted environment, using CO2 and a strict fertilization regime. Make sure your tank is fully cycled before adding the fish, and don't be tempted to alter or change the pH of your water, or modify your water conditions and parameters by using chemicals of any kind. No need to use RO water or adopt any other procedures that would tend to complicate what should be a simple start to your discus launch. If you plan on eventually having a community tank set-up, carefully research the species of other fish you'd like to keep with the discus, to insure they are able to withstand the higher discus temp of at least 82 F, and that they are fully compatible with discus.
And do a complete and proper quarantine before adding any such tank-mates to your discus tank.

Follow these 'rules', and there's little doubt you will succeed with discus !


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## Mxx (Dec 29, 2010)

Clean water, both in terms of pollutants and bacterial count, is generally advised. 

Some discus keepers choose to keep theirs in relatively acid water 5.0-6.0 to limit the growth of many bacteria, but many hobbyists choose to just change the water a lot rather than trying to mess with changing the acidity of their tap water. 

Proper use of ozone with an ORP redox controller can help keep water very clean by effectively breaking down pollutants, as well as killing any pathogens passing through your reactor. And therefore water changes aren't the only way to improve water quality. Ozone needs to be used carefully however, to ensure you are not exposing yourself or your fish to it.


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## PEdwards (Oct 31, 2016)

arc,

A high tech planted discus tank IS doable if it's planned, executed, and maintained well. One of the crucial things is to get fully grown fish from the start. You absolutely do NOT want to try growing little ones out with high protein food. Doing so is asking for all sorts of trouble. Here's a link to some pictures of my tank back in 2003. 2003 AGA Aquascaping Contest - Entry #66 I did a much lager tank again in 2010 but unfortunately those pictures have disappeared into the ether.

It was a 90 gallon with 300 watts of PC light, 2"-5" of straight Flourite, CO2, full dry ferts, an old-school overflow, and home made sump. Full disclosure: I let the chain swords grow out a lot in anticipation of the photo shoot. Normally that whole area was covered in Glosso so the fish had ample room to peck at food on the bottom. The whole foreground required frequent and thorough cleaning to keep from accumulating food. A sand substrate for the foreground is very highly recommended.

On the topic of soil and sand vs. only inert substrate. I did my master's thesis on using soil and clay-based mixtures for growing aquatic plants. I can say with surety that any substrate with enough organic matter in it will go anaerobic within the first inch, maybe even less depending on grain size. Keeping full adult discus in a tank with soil is technically possible (I've done it) but it must be done with care and careful consideration. If this is your first planted discus tank I'm going to second the recommendation of using an inert, dense, substrate material such as Flourite for your planted zones. Find a good 2mm grain size quartz/silica sand to use for the unplanted areas. A local well drilling/supply company should have it. The stuff I used in my research went under the brand name Colorado Sand. Absolutely do not use fine sand like pool filter stuff.  It's too fine to clean effectively and has terrible diffusion which leads to anaerobic areas. 

What Mxx said about ozone is correct, but in my experience is an unnecessary expense and potential hazard. Good aeration when the lights are out will go a long way toward stimulating beneficial bacterial breakdown of dissolved organics. In addition to regular water changes and filter maintenance. 

<edit> Here's a link to a tank the Senske brothers did in 2004. In my opinion it's the perfect planted discus tank.
http://showcase.aquatic-gardeners.org/2004/show141.html

Hope this helps,
Phil


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## Mxx (Dec 29, 2010)

Hi Phil, that was a great looking tank you had! And there were a few interesting points you made there which perhaps could be worth discussing further as you sound quite knowledgeable and experienced about some of these. 

When you are talking about a soil substrate with organic matter, does that mean you are including mineralized topsoil within that category or not? So far as I'm aware, if it has fully mineralized (via the recommended cycling process), then decomposition will have completed and therefore you needn't worry about it getting badly anaerobic? I've also heard that the fears of anaerobic substrate are a bit overblown, and that tank crashes due to hydrogen sulfide gas release or for other reasons are actually exceedingly rare. 

Anaerobic bacteria are even considered highly beneficial by many, including in the reefing world where they are actively encouraged with live rock or deep substrate beds, as the anerobic bacteria are what rid your tank water of nitrates. Plants seem able to cope with it quite well many people advise, and some of the organic processes happening in the anaerobic layer are what free certain critical nutrients such as iron into forms which are useable by plants. And for that reason plants will send roots into the anaerobic zones, where the plant roots also actively amend the chemistry of the substrate by themselves injecting both oxygen and co2. 

My understanding, though based on what scant information I could find, was that the oxidation of the dissolved organic compounds (apart from nitrogen compounds) by oxygenated water and/or bacteria is a very slow process. Thus, in most any tank with greater than minimal stocking levels the rate of oxidation will be slower than the rate of buildup of these compounds. And generally this is why frequent water changes are required if you have sensitive fish. But even with water changes every few days, during those few days these compounds are still building up and the water quality is therefore deteriorating continuously. And therefore, if you'd like for your water quality to be at 100% or close to that at all times, then it makes sense to use ozone meanwhile. 

I thought you could by the way get pool filter sand in nice consistent grain sizes such as 2mm. I haven't used it myself as the only PFS I can find anywhere around here is an unsightly yellowish-brown colour.


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## PEdwards (Oct 31, 2016)

Mxx said:


> Hi Phil, that was a great looking tank you had! And there were a few interesting points you made there which perhaps could be worth discussing further as you sound quite knowledgeable and experienced about some of these.
> 
> When you are talking about a soil substrate with organic matter, does that mean you are including mineralized topsoil within that category or not? So far as I'm aware, if it has fully mineralized (via the recommended cycling process), then decomposition will have completed and therefore you needn't worry about it getting badly anaerobic? I've also heard that the fears of anaerobic substrate are a bit overblown, and that tank crashes due to hydrogen sulfide gas release or for other reasons are actually exceedingly rare.


Yes, that includes mineralized top soil. Mineralizing it is important as it helps break down the more easily accessed materials, but it doesn't break them all down. There are still organic compounds in the way of small particles of plant matter and such. Those will still be used as a source of carbon for the bacteria in the substrate, they just won't grow as quickly as they would in non-mineralized material. 

Fear of tank crashes due to anaerobiosis in tanks is valid up to a point. In normal tanks regular substrate cleaning helps to mitigate it quite a bit. Getting a good deep cleaning without causing a huge mess or disturbing the substrate ecology is difficult to say the least in a substrate with soil underlayers. Keep in mind that water diffusion through sand and other substrate materials is a very slow process. Even with 2mm sand caps I found that only the upper 0.25 to 0.5 inches of my soil treatments remained oxic, and that was primarily due to plant roots. It's safe to assume that with a 1" sand cap only the top 0.5 inch is going to stay somewhat aerobic/oxic and the rest is going to be anaerobic. 

The main concern with this is not the fish, but the plants. Their roots require oxygen for both metabolism and to release into the substrate as a means of protection. This means that the plant as a whole is getting less oxygen to build carbohydrates etc and won't grow as quickly. In normal large(ish) grained substrates this exuded O2 diffuses relatively well in the rooting zone. Since mineralized soil is small grained and "thick" for lack of a better word, diffusion is going to be much much much slower so only the regions right next to plant roots is going to be oxic. This can be hard on plants, especially new ones without robust root systems. 



Mxx said:


> Anaerobic bacteria are even considered highly beneficial by many, including in the reefing world where they are actively encouraged with live rock or deep substrate beds, as the anerobic bacteria are what rid your tank water of nitrates. Plants seem able to cope with it quite well many people advise, and some of the organic processes happening in the anaerobic layer are what free certain critical nutrients such as iron into forms which are useable by plants. And for that reason plants will send roots into the anaerobic zones, where the plant roots also actively amend the chemistry of the substrate by themselves injecting both oxygen and co2.


Anaerobic denitrification is an exceedingly slow process over time. Unless fresh sources of NO3 are introduced to the anaerobic zone, the bacteria will begin consuming other elements such as iron, manganese, and sulfur. That's why most folks use external denitrifers, if they use one at all. 

You're correct, anaerobic reduction of iron and manganese do help supply those to plant's roots. However, when those reduced compounds diffuse up into the rooting zone they're oxidized again and consume some of the O2 the roots are putting out (chemical oxygen demand). It's the exudation of organic acids by roots that helps make those oxidized minerals available again. There's a whole huge cycle there that I don't have time to talk about at the moment. Long story short, only some of the reduced beneficial elements are made available to plants via anaerobiosis. It's a lot easier to add them to the water column where they're more easily absorbed. 



Mxx said:


> My understanding, though based on what scant information I could find, was that the oxidation of the dissolved organic compounds (apart from nitrogen compounds) by oxygenated water and/or bacteria is a very slow process. Thus, in most any tank with greater than minimal stocking levels the rate of oxidation will be slower than the rate of buildup of these compounds. And generally this is why frequent water changes are required if you have sensitive fish. But even with water changes every few days, during those few days these compounds are still building up and the water quality is therefore deteriorating continuously. And therefore, if you'd like for your water quality to be at 100% or close to that at all times, then it makes sense to use ozone meanwhile.


As long as there's sufficient oxygen, the breakdown of organic molecules is relatively fast in microbiological terms. However, it's not typically fast enough to handle the load in a normal tank. That's why we do water changes and use certain chemical filtration media. Keep in mind that tannins and humates are all organic compounds and fish from blackwater systems are adapted to having lots of them in the water. It's the stuff like proteins and other products of waste degradation that are the problem as they contribute to nitrogen and phosphorus build up as well as deoxygenation of the water (biological oxygen demand). 



Mxx said:


> I thought you could by the way get pool filter sand in nice consistent grain sizes such as 2mm. I haven't used it myself as the only PFS I can find anywhere around here is an unsightly yellowish-brown colour.


Most retail sources of PFS are that tiny grained brownish-yellow stuff you've found. That's why I suggested going to a well supply company as they use the 2mm stuff to pack the annulus (place where it actually draws water) of a well. The Home Depot type PFS is far too small to allow good diffusion and will go anaerobic very quickly.

Hope that helped a bit. Substrates are a very complex system that would take a looong time to fully discuss. Time to get ready for work.

Cheers,
Phil


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## Mxx (Dec 29, 2010)

Very helpful I think, thanks!


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