# Keeping nutrients out of water column?



## Grah the great (Jul 3, 2013)

Hi everyone! Long time no post. I was doing some research on water gardens and found that, for containers, one site recommended _not _doing water changes when algae turned up. According to the site, if water changes were withheld, the algae would eventually run out of nutrients in the water column and die off while the plant(s) would still be supplied with nutrients at their roots. My question is, would this actually work in an aquarium? I was going to use a roughly 2 inch thick soil mixture consisting of equal parts sand (for aeration), clay cat litter (to absorb nutrients), and perhaps top soil (not sure if the soil would serve any useful purpose). All fertilization would be performed via root tabs. Thanks


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## minorhero (Mar 28, 2019)

Grah the great said:


> Hi everyone! Long time no post. I was doing some research on water gardens and found that, for containers, one site recommended _not _doing water changes when algae turned up. According to the site, if water changes were withheld, the algae would eventually run out of nutrients in the water column and die off while the plant(s) would still be supplied with nutrients at their roots. My question is, would this actually work in an aquarium? I was going to use a roughly 2 inch thick soil mixture consisting of equal parts sand (for aeration), clay cat litter (to absorb nutrients), and perhaps top soil (not sure if the soil would serve any useful purpose). All fertilization would be performed via root tabs. Thanks


I think when most of your leaves are above the water you can afford to let algae run its course. When the leaves are below the waterline then it getting covered in algae will effect the plant. It can not photosynthesize as well with leaves covered in algae. Plus those leaves will never recover. Its an interesting idea but I don't think it carries over as well to the aquarium.

Unrelated note: Is that a pygmy sunfish in your avatar picture?


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## fpn (Mar 28, 2018)

I think this also depends on the type of algae - for example if you look at this guide for green dust algae then leave it alone, pretty much sums it up, but there are plenty of algae that take advantage of an inbalance and the algae will basically win unless we fix the inbalance.

http://www.theplantedtank.co.uk/algae.htm


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## Grah the great (Jul 3, 2013)

minorhero said:


> I think when most of your leaves are above the water you can afford to let algae run its course. When the leaves are below the waterline then it getting covered in algae will effect the plant. It can not photosynthesize as well with leaves covered in algae. Plus those leaves will never recover. Its an interesting idea but I don't think it carries over as well to the aquarium.
> 
> Unrelated note: Is that a pygmy sunfish in your avatar picture?



Yep...that's a pygmy sunfish  I had not thought about that detail about the algae encoating the leaves...




fpn said:


> I think this also depends on the type of algae - for example if you look at this guide for green dust algae then leave it alone, pretty much sums it up, but there are plenty of algae that take advantage of an inbalance and the algae will basically win unless we fix the inbalance.
> 
> James' Planted Tank - Algae Guide



Bummer


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## Desert Pupfish (May 6, 2019)

+1 with minorhero & fpn that the algae could choke out your plants if it doesn't clear quickly on it's own. Green dust algae is fine, IMHO, especially if you've got some algae eaters like snails & otos to help keep it under control

Re your substrate: I've heard nothing but horror stories about kitty litter turning into a soupy mess. SafeTsorb is basically the same thing--a fired clay--that lasts forever and plants seem to love. I've used it in two tanks now as a cap for potting soil and it works great--though the soil can release a lot of nutrients at the beginning that can, of course fuel algae. But with a lot of fast-growing plants & floaters and water changes as needed, the plants soon get the upper hand. I don't see any advantages to mixing substrates, as they tend to settle out into layers anyway. But soil capped with sand or STS seems to work well for most people. 

Are you looking to do a low maintenance natural tank that doesn't require a lot of water changes? If so, check out Diana Walstad's work. And Dennis Wong's site https://www.advancedplantedtank.com/ is a great beginners guide that compares various substrate options and their pros & cons.


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## OVT (Nov 29, 2011)

In any case, you will find that preventing nutrients from soil and root tabs from escaping into the water column is night impossible. Moreover, decaying leaves, wood, fish food are all sources of nutrients. And who knows what gets absorbed from the air.


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## Grah the great (Jul 3, 2013)

Desert Pupfish said:


> +1 with minorhero & fpn that the algae could choke out your plants if it doesn't clear quickly on it's own. Green dust algae is fine, IMHO, especially if you've got some algae eaters like snails & otos to help keep it under control
> 
> Re your substrate: I've heard nothing but horror stories about kitty litter turning into a soupy mess. SafeTsorb is basically the same thing--a fired clay--that lasts forever and plants seem to love. I've used it in two tanks now as a cap for potting soil and it works great--though the soil can release a lot of nutrients at the beginning that can, of course fuel algae. But with a lot of fast-growing plants & floaters and water changes as need, the plants soon get the upper hand. I don't see any advantages to mixing substrates, as they tend to settle out into layers anyway. But soil capped with sand or STS seems to work well for most people.
> 
> Are you looking to do a low maintenance natural tank that doesn't require a lot of water changes? If so, check out Diana Walstad's work. And Dennis Wong's site https://www.advancedplantedtank.com/ is a great beginners guide that compares various substrate options and their pros & cons.



I wasn't really looking for that...I wanted to experiment with CO2. Would a mix of 2 parts safe t sorb (or perhaps turface MVP?), 2 parts sand, and 1 part top soil work well?


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## mootay (Feb 16, 2015)

My experience with root tabs is that they start disintegrating the moment they touch the water. They can be extremely difficult to bury. An alternative to root tabs, which possibly last longer, is osmocote in gel capsules. I tried this method and found that air inside the capsules caused them to float to the top... pack them with something to fill the gaps maybe?

Sent from my Moto Z3 Play using Tapatalk


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## Desert Pupfish (May 6, 2019)

Grah the great said:


> I wasn't really looking for that...I wanted to experiment with CO2. Would a mix of 2 parts safe t sorb (or perhaps turface MVP?), 2 parts sand, and 1 part top soil work well?


If you use soil, you'll want to cap it with either sand, STS or Turface. If you try to mix things up, the larger sized substrate will end up migrating to the surface, and your soil might end up in the tank water or sitting on the surface. Think of it like you're making lasagne--you want to keep things in layers....



mootay said:


> My experience with root tabs is that they start disintegrating the moment they touch the water. They can be extremely difficult to bury. An alternative to root tabs, which possibly last longer, is osmocote in gel capsules. I tried this method and found that air inside the capsules caused them to float to the top... pack them with something to fill the gaps maybe?
> Sent from my Moto Z3 Play using Tapatalk


I make DIY Osmocote gel caps, and find they work well. I put some SafeTsorb in with them so I'm not putting too much fertilizer in one spot, and on the theory that the STS will absorb the Osmocote as it dissolves and slow its release. And yes, they will float--I take a pin and poke a small hole in the top & bottom, and hold it underwater for a moment to allow the air to bubble out before sticking it under the substrate. If you don't, they'll pop right back up to the surface.

There are a number of threads on here about making your own DIY root table by putting Osmocote inside a ball of red clay. Red clay has a lot of iron--another plus. I tried looking for plain red potters clay, but everything I could find had plasticizers or preservatives in it, but didn't say what they were. Wouldn't want that in my tank. If you're lucky, you can just dig some clay up in your yard....


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## Grah the great (Jul 3, 2013)

Desert Pupfish said:


> If you use soil, you'll want to cap it with either sand, STS or Turface. If you try to mix things up, the larger sized substrate will end up migrating to the surface, and your soil might end up in the tank water or sitting on the surface. Think of it like you're making lasagne--you want to keep things in layers....



So...could I just use safe-t-sorb as the substrate so long as I keep up with fertilizing?


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## Desert Pupfish (May 6, 2019)

Grah the great said:


> So...could I just use safe-t-sorb as the substrate so long as I keep up with fertilizing?


Yep, many people do. Lots of thread about that on here. And even more on the soil vs inert substrate debate. Dennis Wong's site does a great job of covering the pros & cons of both.

If you go with STS, it helps to rinse it, though I've found I can rinse it til the cows come home and the rinse water still won't run clear. I usually pour it from some height into a bucket on a windy day which does a better job of getting rid of any dust than rinsing, IME. But even if you don't, I've found it may kick up a little dust when you plant or otherwise disturb it, but it quickly settles back down w/o making a mess.


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## Grah the great (Jul 3, 2013)

Desert Pupfish said:


> Yep, many people do. Lots of thread about that on here. And even more on the soil vs inert substrate debate. Dennis Wong's site does a great job of covering the pros & cons of both.
> 
> If you go with STS, it helps to rinse it, though I've found I can rinse it til the cows come home and the rinse water still won't run clear. I usually pour it from some height into a bucket on a windy day which does a better job of getting rid of any dust than rinsing, IME. But even if you don't, I've found it may kick up a little dust when you plant or otherwise disturb it, but it quickly settles back down w/o making a mess.



I have no beef with a little dust


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## mootay (Feb 16, 2015)

there's some very unusual substrate choices out there.. i feel a bit ordinary with my lava rock and laterite.

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## reddhawkk (Dec 28, 2011)

I gave up rinsing STS and just put it in and run a filter with floss for a few days to clear it up.


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## Andy H (Nov 14, 2019)

Something else to consider is what nutrients are being used by the algae and their behavior in soil. Ammonia and phosphates are usually associated with algae outbreaks. 

Nitrogen is made available to plants as ammonium or ammonia through microbial decomposition of organic matter in soil. The proportion of ammonium to ammonia in the soil and water depends on pH. As the pH goes, ammonium will convert to ammonia and vice versa. Ammonium theoretically should not leach into the water column as readily as ammonia because it is a positively charged cation and would be attracted to the cation exchange sites within the soil and clay. 

Phosphorous is also a product of microbial processes on organic matter. Phosphorus is used by plants in the forms hydrogen phosphate and dihydrogen phosphate. Plants can only take up phosphorus dissolved in the soil solution, and since most of the soil phosphorus exists in stable chemical compounds, only a small amount of phosphorus is available in the soil water solution for the plant at any given time. 

I have found that even though I don't like to do water changes they are the first or second thing I did when I had a bacterial bloom or an algae overgrowth.


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## AbbeysDad (Apr 13, 2016)

I came to this party late so please forgive me if I'm repeating what you've already learned.
We really don't want ALL nutrients removed from the water column as many plants depend on it...java moss, java fern, anubias, all stem and floating plants... So, although we use plants (especially fast growing floating plants) to aid in purifying water, we need nutrients in the water.


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