CO2 injection and water change

[crazyred]

Okay, I never thought to ask.....do you turn off your CO2 injector (be it pressurized or DIY) during your PWC?? It never even occurred to me, I just left mine on during a PWC and shortly thereafter I had a mass die-off of previously healthy fish. 8O I got to thinking....wouldn't the CO2 concentration go up considerably (and consequently a reduction in O2) when the volume of water is reduce by 30-40% or so in the tank? I'm wondering now if this is what killed my fish!!!

So, what's the story? Do y'all turn yours off during your PWC? Do you think this could explain me recent tank disaster? I've just never seen or heard any instruction on what to do with the CO2 injection during a PWC. If it bad, shouldn't there be some kind of warning? 8O

 

[rich311k]

CO2 levels have nothing to do with O2 levels. There was no way your lessened water levels were in the tank long enough fof the C)2 to build to hazardous levels before you filled back up. I do not disconnect my CO2 when doing a water change. The act of refilling the tank would gas off any extra CO2 anyway.

 

[tbonem91]

the only problem would be a PH or KH swing during a large water change - next time you do one, measure your tanks PH and KH, then the water you're adding - if there is a large difference, then doing a large water change can cause a lot of harm to the fish

 

[crazyred]

Yeah, I thought of that too. My water is pretty well buffered (120 ppm kh) and the pH of the tap water is the same as that in my tank (7.1-7.2), but could it have had a significant pH shift that I wasn't aware of with the CO2 still running (maybe?).

I'm still trying to explain my deaths....I can't help but feel it had to do with the CO2 in some way, shape or form, but I'm still not sure. I'm going to put it back on my tank, but I'm going to monitor it a lot closer.

 

[rich311k]

The CO2 would not cause a KH swing. Unless you buffer the tank the KH in the tank and in your tap will be close, unless you went a long time between changes. A PH swing not do to to KH would not make a difference to you fish. Mine swings everyday by at least a point.

 

[crazyred]

Rats, I was hoping that this solved the mystery. Oh, well....the fish I have are doing well so far and I'm getting ready to try again with some rams....I miss those little guys.

What should I watch for with my DIY CO2 set-up....any other tips or precautions?