jetajockey
come get me tang police!
How so? We're speaking strictly of species which are indigenous to the area they are released in and are an integral part of the ecosystem.
There's a general sentiment that even native fish species once kept in aquaria should never be released back into the wild primarily from the risk of introducing pathogens or something to that effect. I've seen it posted time and again but I don't know what kind of credibility it has. FWIW though the government also promotes stocking programs locally with hybrid fish, if that means anything.
Anyhow, my concern with a heavily stocked tank like that, in essence a feeder tank, would be o2 depletion and a bunch of toxins being produced. But if everything checks out through the nitrogenous waste tests and it has plenty of aeration then it could've been someone nuking the tank.