I have a very big gulper in with two Oscars and there is no way it could swallow them. I've had it for three years now and no problems. Yes it is true that gulpers can swallow very large fish they cannot swallow fish who's gerth is larger than their mouths. The key to keeping them with tank mates is the fish must be larger, top to bottom, than the gulpers mouth can open. Example: a gulper has no problem swallowing an arowana much larger than it's self because the arowana is long and slender but that same gulper could not swallow say a pacu because the lenght of the pacu, top to bottom, would exceed the gulpers mouth. I'm at work now but I'll post pics later if you want, so you can see what I'm talking about. Hope that helps.
