DIY CO2 and fish health

[blueether]

Don't know what section to put this one under so it's in the catch all 'freshwater'...

Anyway I decided to try and get my plants in my all-in-one ~55l planted tank looking and growing a bit better. This started by putting two cold cathode tubes above it (approx 30w - yes I know...) three or four days ago. This started the BBA growing and a little green spot algae. So today I rigged up a DIY CO2 system after a ~20% w/c.

Results:

Within 1 min of the first bubbles going through the venturi on the powerhead my last two grey mullet are flashing, shaking their heads and acting very stressed. Thinking this could be either the CO2 or the w/c I disconnected the CO2 (as I cant really get the water back that I changed out) and within 2 or 3 min they are acting again fine.

So time to experiment... connect the CO2 back uo and press the bottle to get some CO2 in to the tank, and again within seconds of the bubbles going through the powerhead the mullet are starting to act stressed and are shaking their heads.

Conclusions:

Some fish really don't like a shift in the CO2/pH

[Godly3vil]

You sure the venturi isn't pulling any of your co2 mix into the tank? Using a venturi on diy isn't very good I thought as it can pull the mix into the tank just as it pulls air into it.

[Dachende]

Only thing I can think of is that your setup may be saturating the surrounding water with c02 and not spreading it throughout the tank

here's a good version of a DIY Reactor for c02 if that is the case ? or if you're interested in trying another diffusion method.

Lots of other info there too.

http://www.qsl.net/w2wdx/aquaria/diyco2.html#3