I'm gonna qualify my earlier comment on this idea, i.e. that it seems like it would be okay.
If I were in a position where I needed it, I could see eating an aquarium fish. BUT...it would have to come from a clean, well-maintained aquarium, the fish would need to be healthy in appearance, and most importantly of all...it would have to be alive right up to point where it goes under the knife.
Some of you guys are talking about coming home, finding a dead fish floating in your tank and firing up the hot oil! Seriously? That's like eating roadkill.
I've eaten grouse, goose, pheasant, rabbit and deer that were killed by a vehicular impact...but only if I were in the vehicle at the time, or at least saw it happen right in front of my eyes. No way I'm driving along the highway, finding a dead critter and throwing it in the truck for butchering.
There's an old hunter's expression: you kill it, you eat it. I agree with that for the most part, but I also feel that it you want to eat it...you kill it yourself. I don't want to scavenge.
Oh, and I will edit this to add: wild game...birds, rabbits, whatever...are always far superior IMHO to domestic store-bought versions. I would not expect even the healthiest aquarium fish to taste as good as a freshly-caught specimen right off the hook.