New DIY CO2 reactor, fish gulping air??

There is a lot of speculation going on here without any facts. Guessing is going to get you into more trouble. What are your numbers both before and after the problem?

GH?
KH?
Ph?
NH3
N02
NO3
Temp

I could guess too and say that it sounds like a Ph crash but that is not helping you.
 
Its hard to figure that one co2 diy 2 litre can cause gasping fish. I have 5 x 2 litre on my 66g. Ph is 6.8 as of this morning. KH is 3.9 dh. I am pumping about 19 ppm . Fish are fine. I have a 4 inch clear plastic spice bottle that I run my spray bar through, I feed the co2 line through the bottom of it the bottle. I tried feeding the line directly into my canister filter, however, I couldn't get the co2 level higher than 10 ppm, because the co2 was not staying in the water long enough to affect the ph.

The situation described above sounds strange. I would not suspect your co2 system as the culprit. Perhaps amonia, nitrite, and nitrates?
 
Guys, I don't have the numbers but my DIY CO2 experiment is over. The water in the 55g tank has always been rock solid stable. When I put the CO2 in, the fish gasped. When I removed it they did not. That is enough for me. Thanks for the commentary.

If I approach this again, I'll get before and after measurement of everything.

-Cheech
 
Wow, I had DIY CO2 on a 29 gallon and everything went well. Er, I know you neglected to d any testing of the water, but could you tell us what you put in the DIY mix itself? I mean to ask, what recipe did you use?
 
2 litre bottle about 2/3 full of water, approx 2 cups of sugar and a half tsp or so of bread yeast. Mix was bubbling vigorously within an hour. I fed the cO2 bubbles into the intake of the canister filter.
 
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