Low oxygen?
 

My wife lost a couple of clowns in her 14 gallon biocube which had been doing great, eating well etc. At first we thought it may have been because of a spike in nitrates because she was removing the bioballs a few at a time. I checked the nitrates and they were around 10 ppm which I doubt would be high enough to kill a healthy fish. Talking to another Canreefer last night I began to suspect that they may have died because of low oxygen levels in the water. Just wondering if anyone else has experienced this problem with nano tanks or if its even a possibility? BTW, there is still a goby in the tank and it seems to be fine. It just seems weird that two fish should die at the same time.

IMO, unless you had a party with 20+ people over and kept all the windows and doors closed (not sure how they all left :)) then no, it's not going to be low O2. This assumes of course that there is some water movement in the tank and there isn't a film of anything across the top of the water.

Ha! Nope, no major parties recently! All the other parameters were good. How high would nitrates have to be to kill fish?

Really high! For a length of time. Probably not nitrates.

I've been battling with high nitrates myself and I can tell you clowns can be very hardy and high nitrates are not gonna get to them at all, well for a short period of time though. If you keep high nitrates for a long period of time, not only clowns will be affected but all other fish as well.

How long did you guys have the clowns? Its pretty strange both clowns died at the same time. As i said before, those little guys can be and are pretty hardy, they can take a lot of abuse if they are healthy. My guess is they were already sick from before.

We have had the clowns since late October. Like I said they were healthy,eating well and very tame. They started acting strange one day and the next day they were dead.

In what way ?

They just quit eating.

The odd time this has happened to me was after I left frozen food on the counter for a few hours... Then used it. Go bacteria!