# Diffusion of CO2? Getting frustrated



## Batt4Christ (Apr 30, 2011)

So, the tank is a standard 55g, Odysea 3-bulbe T5 HO fixture.

CO2 setup is a 20lb bottle, Hydor Regulator and glass bubble counter, and a Hydor Turbo Co2 Diffuser (apparently they don't sell/market them here in the US - I got mine as part of a package deal from an individual).

Anyway - if I set the regulator to 2-3 bubbles per second, the Hydor diffuser puts out very tiny bubbles. BUT, after several months - I just can't get my CO2 levels up to where they need to be. Using a drop checker (with the correct 4dKh solution), I couldn't get levels beyond the blue-green color. Checking my pH, my tap water is 7.4. With CO2 set to 2-3 bps, The pH would drop to 7.3 over the course of several hours. Turning it up to 5-8bps, I could sometimes get the pH down to 7.1-7.2.

A couple of weeks ago, I decided to see how high I could turn up the CO2 without causing the little Hydor diffuser to cavitate and start throwing big bubbles. I actually got it to where the bubbles in the bubble counter were way too fast to count - and after 24 hours, my pH had dropped to 6.9. The liquid in my drop checker was actually fairly green. 

So I back off the CO2 to where I can count the bubbles (approximately 6 bps) and by the next day, pH was back to 7.1.

I have experimented with placement of the diffuser, from right under my Emperor 400 HOB filter, to well away from any filters (and everywhere in between). Only way I can get CO2 levels up is by running an insane amount of CO2. Obviously the Hydor is extremely inefficient.

A buddy just recently set up the same size tank, running pressurized CO2, but the reactor/diffuser he has is a Mr. Aqua Turbo 400. He runs 3bpm and his CO2 levels come up considerably more. His drop checker is green at that point. His pH drops down to 6.4 at that injection level.

So I'm at a loss. I think a 20lb CO2 tank should last more than 5 months too. 

I have been looking at the RedSea Reactor 500. It has mixed reviews, though mostly positive. I don't have a canister filter (per-se) - I do have a Marineland HOT filter that hangs on the back - but it has all rigid tubing and no provisions for any hose connections.

I have pondered getting a regular canister filter, but my budget really isn't there.


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## The Trigger (Apr 23, 2012)

i mean if you only have a hob theres another option than getting a canister filter. and its this...http://www.amazon.com/Hagen-Elite-U...D7D4/ref=sr_1_1?ie=UTF8&qid=1337119763&sr=8-1

i used that before i got pressurized co2 and a canister, and it worked extremly well to diffuse the co2. i simply placed the diffuser i had at the time under it so the already tiny bubbles would be broken up even more. i had the same problem as you. i was getting too much loss of co2 at the surface.


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## Batt4Christ (Apr 30, 2011)

The Trigger said:


> i mean if you only have a hob theres another option than getting a canister filter. and its this...http://www.amazon.com/Hagen-Elite-U...D7D4/ref=sr_1_1?ie=UTF8&qid=1337119763&sr=8-1
> 
> i used that before i got pressurized co2 and a canister, and it worked extremly well to diffuse the co2. i simply placed the diffuser i had at the time under it so the already tiny bubbles would be broken up even more. i had the same problem as you. i was getting too much loss of co2 at the surface.


I'm wondering if connecting the CO2 line to the venturi port on that filter would get the job done? Then again, it might just spit out bubbles.

So - did you put this just next to your usual diffuser for it to basically circulate the fine bubbles?


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## The Trigger (Apr 23, 2012)

Diffuser under it. It intakes from the bottom. This would break down the small bubbles into A micro mist, than it would disperse it across the tank. Your problem is that the bubbles aren't staying in the water long enough for them to be absorbed into it. Theyre just rising to the surface too fast. Hence your low co2 level. A canister filter with a spray bar would fix this problem by itself since you can just tip the spraybar slighly downward to force the bubbles down. But that mini filter will work wonders if you don't have a canister.


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## Batt4Christ (Apr 30, 2011)

Hmmm... I did try putting the Hydor directly under the intake of my HOB (Emperor 400). That didn't help - if anything, it hurt. I suppose that is because of it getting gassed off in the external "open" filtering/biowheel/water jets that keep those wheels spinning.

So - that little filter, placed directly above the Hydor.

How would this compare to getting the Red Sea Reactor 500 (other than more money, but possibly a more permanent option)?


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## AaronT (Apr 26, 2004)

Your HOB is the problem. Once you get some evaporation you are getting major surface agitation which = CO2 gas off. Some surface agitation is good, but HOB filters are just not good for planted tanks with CO2 for this reason.

You can combat this with fast diffusion. Use a powerhead and feed the CO2 into the inlet of the powehead. The impeller breaks up the CO2 into small bubbles and then pushes it around the tank. This method has become known as "misting" and works rather well. 

Regardless, I suspect circulation is a big culprit as well. Those diffusers just bubble upwards. You need some powerheads to increase flow in the tank to distribute that CO2. If you want to keep the diffuser try putting it under a powerhead as Trigger suggested. The Hydor Koralia nano 425 gph would be a good one for that size tank. You could even use two on opposed sides of the tank.


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## Batt4Christ (Apr 30, 2011)

Yeah- I know about the HOB and surface disruption. That's why I keep the water level at the absolute max the tank can hold It cuts down the surface disruption considerably.

Of particular note - my buddy's tank that I mentioned in the opening post - same size tank, with a Penguin 350 HOB and another HOB (can't recall which model). He is using the Mr. Aqua Turbo 400 - and getting superb results from FAR less CO2 than I'm using. Looking at his tank, he has more surface disruption than I have.

As an experiment, I have moved the Hydor to directly under my HOT Magnum's intake. I'm hoping that some of the little bubbles will actually get sucked in and the small canister will work as a sort of reactor.

Another experiment I'm looking at - a DIY spraybar for the HOT. I found someone's plans that included adding a hose nipple to the outflow to hook the CO2 line to. 

Thanks for the input.


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## Batt4Christ (Apr 30, 2011)

How hard would it be to adapt this to my HOT Magnum or a powerhead?


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## gr33nthumb (Oct 18, 2011)

Somewhat of an old thread here but I'll throw some ideas out! Before I moved my canister from the beast tank to the planted to run the Rex PVC reactor I made, I used a marineland 1140 powerhead I believe it was. Mounted it horizontal at the bottom of the tank, ran vinyl tube up and out to the reactor then just ran tube back into tank. For inlet and outlet I used various 90 degree barbed plastic elbows as needed. The cost of the whole setup was amazingly cheap and worked great. Worked so good that I kept the flow rate I was using on my ceramic diffuser and had my fish gassed in a couple hours! Hope that helps, it is a cheap alternative! Another thought is to check out RIO pumps on ebay, very good and you can grab one for cheap to do the same thing as a powerhead.


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## kimcadmus (Nov 23, 2008)

Even if the CO2 is diffused it is not only about keeping in the tank but circulating it efficiently. If you want a cheap unobtrusive easy mod that costs less then $10 check out this thread. It is much smaller than a reactor in your tank. I have been using it for years thanks to my friend niko. I takes me 6mos to get through a 10lb bottle. Works on small and large tanks. I have had it in 10g and 75g tanks.

Here is the thread:
http://www.aquaticplantcentral.com/...y-super-efficient-co2-reactor.html#post327883

Here is the pump description ( the petco thread link no longer works):
A-130 Elite Mini Filter
http://www.hagen.com/uk/aquatic/product.cfm?CAT=1&SUBCAT=107&PROD_ID=01001300030401


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## Vinman409 (Jan 23, 2011)

i made a diffuser for a 100 gal tank by using an old gravel vac tube i put a cap on the bottom of it drilled a hole in the cap for the co2 line put the line to the top of the vac tube added a wood air stone or whatever and two bio balls inside drilled a hole 1/2 inch in the vac tube 3/4 inch above the cap and it works good


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## Vinman409 (Jan 23, 2011)

just connect it to a canister filter inlet tube


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## Vinman409 (Jan 23, 2011)

its easy to connect it to a hot mag filter i also did that works fine


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