when I first started getting into the hobby I'd say around march I had two jack Dempsey's in my tank. They absolutely terrorized and almost Killed every other fish in the tank over night! Oscars and electric blue acaras. I did not have a spare tank at the time and did not know you could give back to fish store. Anyhow I have a pretty big outdoor pond that is not heat regulated or anything(I live in jersey so the weather has fluctuated from high fifties to almost 100 since then) I had not seen them since they got thrown in the pond. Well low and behold today I go outside and the pond is clearer then usually because my dog hasn't been rampaging through it lol andd there is one of the dempseys about ten inches big with a small goldfish in his mouth lol. They are very resilient fish to say the least!