# HOB and CO2



## OVT (Nov 29, 2011)

How "best" do you want.

The easiest is in tank diffuser, something like that: https://www.amazon.com/Rhinox-Diffuser-Healthy-Aquarium-Plants/dp/B005MLTRR4/ref=sr_1_12?s=pet-supplies&ie=UTF8&qid=1518823889&sr=1-12&keywords=co2+diffuser


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## Nubster (Aug 9, 2011)

In tank diffuser like this one as an example....


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## Tiger15 (Jan 7, 2018)

The most efficient co2 dispersion is the reactor type that is driven by a canister filter. Any diffuser type with a ceramic disc is less efficient and gradually get clogged up creating excessive back pressure. Since you are on hobs, you need a power head driven reactor such as Tunze reactor or diy following Tom Barr Venturi reactor design.

https://www.amazon.com/Tunze-USA-70...pID=31vijaqli4L&preST=_SY300_QL70_&dpSrc=srch

http://www.aquaticquotient.com/forum/showthread.php/13643-Tom-Barr-s-DIY-Internal-Reactor-w-venturi


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## houseofcards (Mar 21, 2009)

Efficiency is a WAY over-rated when it comes to co2. I've been using ceramic discs for 10 years and never had a problem with excessive back presure. If you have an HOB, keep it simple and just use a ceramic disc under the return. ADA knows something about planted tanks and they use ceramic discs on 6 footers.


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## quiquik (Dec 13, 2013)

You can check out this thread and see if this is something you might want to do. When I did this I had 2 HOB 70's that I ran my co2 through using a T fitting and I drilled a second hole the same size as the one you will find on the gray plate because there has to be an open hole for the filter to prime when restarted after maintenance. So there are two holes now in that plate, one for co2 and one for priming, then cut the tip of the chop stick off enough to still fit into the tubing and then stick it in as far as you can, mark the stick with about a 1/8 inch showing out of the tubing then cut that piece, by doing this it will not interfere with the impeller or keep you from putting the plate down all the way where it belongs. Run your tubing through the plate, then stick the chop stick piece into the tubing and push it back into the hole as tight as you can. If you want I could show a pic of what I'm talking about, it's easy. Here is the results and I probably change out the chop stick every month when I do filter maintenance.http://www.plantedtank.net/forums/attachment.php?attachmentid=829882&stc=1&d=1518874896


The thread you can check out is https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNF8PFr4ocF9JtSkVslDfysvOeJePg

This is a 50 gal that I had to tear down due to a broken center brace hence the clamp with the ribbon on it so I didn't accidently hit my head on it or bump into it lol.


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## Tiger15 (Jan 7, 2018)

houseofcards said:


> Efficiency is a WAY over-rated when it comes to co2. I've been using ceramic discs for 10 years and never had a problem with excessive back presure. If you have an HOB, keep it simple and just use a ceramic disc under the return. ADA knows something about planted tanks and they use ceramic discs on 6 footers.


What brand of ceramic disc do you use? The one I used got clogged up within a week creating excessive back pressure that damaged the second pressure gauge of my Milwaukee regulator. Milwaukee user manual specifically warned against ceramic diffuser.


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## Letsfish (Jul 11, 2017)

I am just getting my parts together for a pressurized CO2 set up I am going to run it to 2 tanks a 55 with a Cascade 1500 canister and 29 with a 75 Tidal.The 55 has a UV after it leaves the canister so I`m not sure whether I going to use an inline diffuser or build a reactor.In fact, I`m not even sure where it will go, before or after the UV.I`m going to split the line right after the solenoid with 2 Fabco NV 55-18 needle valves and then run in-line check valves and bubble counters.Here is a few pic of what I am trying to do. The CO2 tank will goat the right of the first pic and it will be between both tanks.


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## KrypleBerry (May 23, 2017)

I use an in tank atomic diffuser and place it right under a power head for distribution. Works like a charm.


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## houseofcards (Mar 21, 2009)

Tiger15 said:


> What brand of ceramic disc do you use? The one I used got clogged up within a week creating excessive back pressure that damaged the second pressure gauge of my Milwaukee regulator. Milwaukee user manual specifically warned against ceramic diffuser.


I've used many different brands with a Milwaukee regulator over 13 years. I've never heard of one blowing out a gauge. If your ceramic diffuser is getting is getting clogged in a week that's a result of your tank conditions. I run mine for usually a few months before I do a bleach bath.


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## ChrisX (May 28, 2017)

I added a HOB to my 50g planted with canister filter, and it gasses off a ton of CO2. 

At 1 bps 24/7, the CO2 was 30ppm prior to the HOB. Adding the HOB, CO2 was in the 5ppm range. In order to overcome the HOB, I had to raise CO2 to 2.5 bps to get it back where it was before. Because of this I had to go back to a 8 hour CO2 cycle.

Water surface agitation is good for adding oxygen, but it also gasses off CO2. I would not intentionally use an HOB for a planted tank, unless I had a really big CO2 tank, or a small aquarium. A power head with a venturi is a much more effective way of oxygenating the water without gassing off co2.

If you dont have a canister, just use a ceramic disk.


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## quiquik (Dec 13, 2013)

5 lb tank lasted me 1 1/2 months with the method I used and dropped my ph just under 1.0.


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## Jeff5614 (Dec 29, 2005)

houseofcards said:


> Efficiency is a WAY over-rated when it comes to co2. I've been using ceramic discs for 10 years and never had a problem with excessive back presure. If you have an HOB, keep it simple and just use a ceramic disc under the return. ADA knows something about planted tanks and they use ceramic discs on 6 footers.


Completely agree.

Here's my first planted tank before I knew anything about them, including even a clue about a layout, but still enough CO2 to grow a fine riccia carpet along with some L. cuba.










And a top down of my current 85 gallon using a pollen glass at the time.


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## ILikeRice (Jul 9, 2017)

I use to put my diffuser under my hob intake before I went inline ^^ Worked for me.


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## Tiger15 (Jan 7, 2018)

houseofcards said:


> I've used many different brands with a Milwaukee regulator over 13 years. I've never heard of one blowing out a gauge. If your ceramic diffuser is getting is getting clogged in a week that's a result of your tank conditions. I run mine for usually a few months before I do a bleach bath.


I am not sure why I have a totally different experience. I blew my Milwaukee pressure gauge in one week and the back pressure was so high that it triggered opening of the pressure relief valve. But I am graceful that Milwaukee sent me a replacement valve. Here is instruction from Milwaukee against using diffuser.

As for hooking up CO2 to AC intake, it may shorten the life of the impeller due to cavitation wearing. If you don't know what cavitation is, here is a link.

https://en.wikipedia.org/wiki/Cavitation


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## houseofcards (Mar 21, 2009)

What kind of conditions did you have in your tank that caused your diffuser to clog up in one week? Do you have any idea how many people use diffusers with pressurized systems, especially on nano size setups and I never heard of this happening. I've used several Milwaukees for 13 years with diffusers so you could see why I'm very confident this is not an issue.


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## Tiger15 (Jan 7, 2018)

I have no dispute that yours and others experience on diffuser is good, but not mine. I called Milwaukee after blowing the pressure gauge in one week and I was advised not to use diffuser.

I bought my diffuser from ebay: 

https://www.ebay.com/itm/4-in-1-CO2...-Plant-Tank-/201639188959?hash=item2ef2a1d9df

It worked for a few days with micro bubbles, but I had to constantly adjust upward the needle valve, building up higher and higher pressure until it brew the pressure gauge and pressure relief valve. I have heavily stocked tank and high waste load. But I suspect I had a bad diffuser but even a good diffuser will eventually get clogged up, and wonder why there are no more complaints.


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## houseofcards (Mar 21, 2009)

Tiger15 said:


> I have no dispute that yours and others experience on diffuser is good, but not mine. I called Milwaukee after blowing the pressure gauge in one week and I was advised not to use diffuser.
> 
> I bought my diffuser from ebay:
> 
> ...


I've never used that particular diffuser, but I know the Fluval One I've had issues with the pressure building up and then blowing off the tubing at the check valve, but this has nothing to do with the diffuser being clogged. 

I generally just use regular glass diffusers lik this One

I suspect there's an issue with the diffuser or your tank if it's getting clogged in a week. Most just clean them every month or so and they don't completely clog.


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## theglassisalreadybroken (Feb 9, 2018)

nah bro just feed that tubing into your intake valve and let the impeller karate chop the bubbles


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## ChrisX (May 28, 2017)

quiquik said:


> 5 lb tank lasted me 1 1/2 months with the method I used and dropped my ph just under 1.0.


Point of comparison.. in similar sized tank, 24oz CO2 tank lasts seven weeks using Griggs. pH drop is 1.5.


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## houseofcards (Mar 21, 2009)

ChrisX said:


> Point of comparison.. in similar sized tank, 24oz CO2 tank lasts seven weeks using Griggs. pH drop is 1.5.


You can't make a general statement like that "similar sized tank" and ignore every other factor. That's just not valid. My in tank co2 diffuser lasted 6 months in my 72G and the tank pearled like mad.


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## ChrisX (May 28, 2017)

houseofcards said:


> You can't make a general statement like that "similar sized tank" and ignore every other factor. That's just not valid. My in tank co2 diffuser lasted 6 months in my 72G and the tank pearled like mad.



I think its the exact same tank. I was getting 3-4x the efficiency with griggs on canister. With a larger pH drop.

Just letting him know. Some people don't care how much they use, I have to conserve because my tank is small.

Its not a scientific comparison, just an anecdote to help him.


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## quiquik (Dec 13, 2013)

I agree that there are more efficient ways to inject co2, but this worked out fine for me because I had no place to put a canister filter, nor did I want to see a diffuser in the tank. So with the filter option that I had two ac 70's and only 15 bucks a pop to fill the 5 lb I was happy and so were my plants, and no micro bubbles to be seen. The tank was also open, no lid, and lights and co2 ran for 8hrs a day. So if one wanted to inject co2 with only hob's as the only option for what ever reason, space, budget, or what ever this was not a bad idea. We kinda brain stormed the whole thing quite some time ago and at the time it was fun and worked pretty well.


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## Tiger15 (Jan 7, 2018)

I have never thought about injecting CO2 directly into the intake of AC HOBs. It is a simple concept and probably works with low bps. High bps will likely cause gurgling noise and shorten the life of the impeller due to cavitation. 

If you don't want to use a canister to drive a reactor, there is an alternative to use a power head as I pointed out in Post #4.

Having started my first planted tank a year ago, I learned that canisters are very popular in planted tanks and I can see why. Canister can easily be hooked up with an inline reactor. Canister provides good circulation without excessive surface agitation to outgass CO2, and the inlet and return tubes can easily be hidden, which is a priority for plant scape folks.

But I am no fan for canister. Canister is PIA to clean, and procrastinating cleaning can lead to anaerobic conditions in power outage. The many O-ring, seals and substantial external plumbing are vulnerable to leak that can drain the tank. In my 30+ years of fish keeping, I use only HOBs or sump, never canister. So I had to look for alternative to disperse CO2 in my planted tank and found a German made Tunze reactor, the only commercial power head driven reactor. 

I am pleased with the Tunze reactor which is quiet and compact, measured about 7" by 1", and not an eye souring piece. Because of its compact size, the capacity is probably no where near the much larger Gregg reactor. It has the advantage of simple design, no external plumbing vulnerable to leak, and no need to prime as required for Gregg. The only requirement is to flip upside down to let go the accumulated air bubble in WC.


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## quiquik (Dec 13, 2013)

There was a second hole drilled into the bottom grey plate for co2 tubing and my bps was to fast to count. No gurgling.


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## burr740 (Feb 19, 2014)

quiquik said:


> There was a second hole drilled into the bottom grey plate for co2 tubing and my bps was to fast to count. No gurgling.


Second that^. Im also in that thread and had good results. Running two 20 gallons that way now except Ive switched to those cheap "diffusers" that look like an air stone.

I can say after nearly 3 years there's no visible effect on the impellers. Might be more brittle than normal by now, break easier if it were bent, idk


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## GrampsGrunge (Jun 18, 2012)

My 32 gallon tank was filtered by a old 1970's Lee's power filter with J-tube intake siphons on the intake, and the DIY CO2 tubing was plumbed into the outflow tube with a small hand soap bottle swirl chamber, ( properly cleaned ) so it was probably the grandfather of all outflow CO2 reactors.

It didn't really have much of any CO2 wastage on it, but at about a bubble every 3~5 seconds I wasn't using a lot on my plants, Water was 7.2~7.4 out of the tap and the tank ran about 6.9 pH.

I could have used the AC 500 on my 48 as a diffuser, but I used a bell jar siliconed to the center brace and directed the flow of a small powerhead across it's opening, also worked well.


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## GrampsGrunge (Jun 18, 2012)

burr740 said:


> Second that^. Im also in that thread and had good results. Running two 20 gallons that way now except Ive switched to those cheap "diffusers" that look like an air stone.
> 
> I can say after nearly 3 years there's no visible effect on the impellers. Might be more brittle than normal by now, break easier if it were bent, idk


The plastic impeller/ bearing is Nylon and rides on a stainless steel shaft, all of which are all pretty impervious to light acids, and what ever possible cavitation is not anywhere near the forces encountered with ship propellers, and should not damage them at all.

All of my present AC filters were bought in the 1990's and they're still plugging along fine today, one of the advantages of living in an area with soft water.

You're introducing the CO2 into the chamber indirectly above the AquaClear's impeller. Actually off to one side. My watching the bubbles come through on my AC 500, they tended to circulate crazily around the perimeter of the impeller chamber before being blown down and sideways under the filter media basket.

It's a hell of a life for a poor bubble of CO2 inside a AC HOB, but you gotta diffuse it somehow :tongue:


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## Tiger15 (Jan 7, 2018)

quiquik said:


> There was a second hole drilled into the bottom grey plate for co2 tubing and my bps was to fast to count. No gurgling.


Can’t pic what you meant a second hole? Do you have a pic.


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## GrampsGrunge (Jun 18, 2012)

Quiquik actually drilled in a second hole in the impeller plate, which helps get rid of the excess air when restarting the AC filter


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## Tiger15 (Jan 7, 2018)

If the co2 is injected into the impeller chamber, the injection is after the impeller, so the gas is not in contact with the impeller and there should be no cavitation. This is very different from injecting into the intake and let the impeller chop up the gas. The AC filter is equivalent to a HOB canister in which the impeller chamber is the inline reactor. There is further dissolution when the gas water mixture is pushed through the filter media. It ought to work, provided there is a tight seal between the tube and the chamber to prevent escape of CO2.

I wonder if there is priming and restarting issue each time the filter is cleaned or there is a power surge?


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## quiquik (Dec 13, 2013)

GrampsGrunge said:


> Quiquik actually drilled in a second hole in the impeller plate, which helps get rid of the excess air when restarting the AC filter


Correct, and it's the same size as the hole that the manufacturer puts in for priming, so all I did was find a drill bit that fit that hole. What was nice is the tubing and chop stick piece fit perfect in that hole. When I get a chance I'll post a pic. In fact there is a pic from burr with the plate and tubing in the manufacturer's hole in that thread. That's how I set it up and then realized the filter had a hard time priming so that's when I drilled a second hole.


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