Dark Cycle CO2 Help!

[Coconutmuffn]

I suddenly seem to have an issue with CO2 accumulation in the water during my dark cycle. Here's my story:

I recently(3 days ago) replaced my Biowheel 280 power filter with a canister filter for better filtration and decreased surface disturbance. I have been running the Hagen CO2 canister with 1/4 tsp yeast for about a month now in this 37 gal tank. Suddenly, tonight, about 2 hours into my dark cycle my fish were all at the top gasping/gilling for air. My CO2 was sky high so I put in an airstone and disconnected the CO2 to bring the fish back around.

Almost everyone is doing fine now, but my question is, how can I regulate this massive accumulation during the dark cycle with the DIY? Will leaving it run, but turning on an airstone or two be enough/too much? For so long I've had such a terrible time keeping CO2 in the tank, now I can't get rid of it. Any suggestions would be greatly appreciated!!

 

[fort384]

I had the same problem with my DIY system. In the AM, after the dark cycle, my CO2 ppm was 100+ (using the pH/KH index). I added a 6" bubble wall to my tank that kicks on 1 hr after lights out, and shuts off 1 hr before lights on, and my CO2 is almost constant at 30-50 ppm, right in the sweet spot so to speak.

 

[mgamer20o0]

you can put a air stone on the timer. i would look into a drop check since they do read co2 levels a lot better. a number of things and throw off the ph kh index. may not be the case in your tank.

 

[fort384]

I use a drop checker as well, but think that the pH/KH index is more accurate. The drop checker reads a very wide range... i.e. it tells your your CO2 is "high" but not how high. There is a big difference in level of concern if you have 50 ppm CO2 vs 120 ppm CO2, but all a drop checker would tell you is it is high.