Who's the culprit?

[jwaechter]

I've lost 5 fish (disappeared - no trace) over the last 2 months from my 55G community tank.

Water conditions are excellent, and no new fish have been added.

Here were the original inhabitants:
2 female bettas
3 black skirt tetras
5 zebra danios
2 cory cats
3 otos
10 platys

None of the fish were unusually large or small, and they all behaved well for many months.

Then 2 of the danios disappeared within a week. A few weeks later and one of the otos is gone (I know they hide very well, but I don't have decorations that they could hide in, and I removed everything but the gravel to do a thorough cleaning.) Now today I noticed that 2 platies are missing and all the remaining fish look stuffed! They didn't swarm to the front of the tank during feeding time, so I think they made their own meal this afternoon!

All of the fish were healthy and acting normally yesterday. There is no trace of the missing fish in the tank.

I'm trying to determine who the culprit is. I'm suspecting the tetras, and would consider giving them away if they are the likely candidate. Are they known to kill/eat platies on a whim? I've got a lid on the tank - always closed. No other pets in the house, and no chance for a bird to be sneaking in for a snack.

I don't over-feed my fish, but I do feed them a little every day except Sunday. So I would not expect them to be so starved that they would attack each other. In fact, I thought they looked "pleasantly plump."

I would chalk up one or two fish over a couple months to misc. health or old-age issues, but 5 fish in 8 weeks is too much. Any idea whodunit?

 

[Zagz]

Have you tested your water parameters? It is possible the fish are dying from some other cause and the other fish are eating the dead fish. I wouldn't expect any of the fish aside from possibly the female bettas to be aggressive enough to attack and kill the other fish. I'd test your parameters and post the results.

Welcome to AA! Pictures of your tank would be great!

 

[theotheragentm]

Tetras are nippers, but they generally won't eat a fish live. Those fish will take the opportunity and feed on an already dead fish. I would check water parameters as it seems odd that that many fish would be weak enough to die. Also I would check the filter to see if remains were sucked into it.

 

[jwaechter]

I checked the water tonight just to be sure.

Ammonia, Nitrite, Nitrate all 0, pH 7.8, temp 78F - just like it always is. I over-filter the water with a HOB bio-wheel and a sponge filter.

 

[eah]

If your tank is properly cycled, I wouldn't expect your nitrates to be at zero. There may be a problem with your water testing kit.