CO2 reactor for small tanks
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I have a 15gal tank that I am trying to get high light to work on (65w cf 9700K) But the problem I have is algae due to low CO2 levels SO what to do?

The tank is using pressure CO2 with a DIY bubble counter. From there it goes to a glass diffuser with a ceramic stone. I could not get the PH to drop no matter how much CO2 I pumped in. SO this tells me I have poor CO2 being dissolved or to much water turbulence at the surface. I think both.

To solve this problem I needed a filter I could submerge and all so use as a CO2 reactor. This is what I came up with. Duetto 100 submersible power filter.
They are really nice little filters. They work like a small canister filter. As you can see the water flow should give this small 15gal tank plenty of filtration.
Here are the parts. I will use the sponge but I have no use for the charcoal canister.
First thing to did is cut a ceramic air stone to a size that will fit inside the filter. I did this with a rotary tool and a course hard stone tool to cut and smooth the cut end.
Next I drilled a hole just big enough to push a 1/8 air line hose thru. I attached the air stone on one end and a 90 degree 1/8 air hose fitting on the other end.
Since I am not using the charcoal canister, that gives me room for the air stone.
Here is the final job. I have installed it today and so far so good. I will do a water test tomorrow and see if the PH has dropped any. It looks like its working. Once every few minutes I see some bubbles come out so its just a matter of get the CO2 bubble count to a level that will cut down on CO2 loss.

Just thought I would share my latest project with you guys. I'll keep you posted on my results.

update 1/24/05
Looks like this is going to work better then I had hoped. My PH dropped form 7.5 to 6.8 . The bubble count is 1 bubble/sec. I still get the spurt of bubbles every couple of min. so I will cut back on the bubble count and see if I can still maintain a PH of 6.8 , which is my target PH level.

update 1/27/05
I have all ways preferred the ceramic air stone to any of the wood stones. They last for ever and make the smallest bubbles. Things seem to be working as planed. Its getting it set to the right bubble count. It looks like setting the bubble count to one bubble per sec. is going to give me PH 6.8. I can see my plants starting to perk up all ready.

update 2/14/05
Well its been three weeks and I have a problem. Its not a biggie, here it is. Its time to clean the filter, to do so I have to take off the CO2 line running to the air stone. When I do this I will loose my pressure in my bubble counter. I wonder if I put a plastic in-line ball valve in the line if I can hold my pressure when I clean the filter. OR will I have to use a brass valve. I have run into problems with some of the cheaper plastic valves not holding up to line pressure.

update 2/27/05
Using the plastic ball valve works just fine. I have cleaned the filter twice using the ball valve to maintain line pressure without any problems. So if you are in need of an alternative way to not only for filtration but a good CO2 reactor all in one unit, This will do the job in small tanks 15gal or less.

Hawk