www.fishbase.org ....but since you are looking at around 25,000+ potential species, you would do best identifying the family of fish in question first...it will narrow your search greatly.
Well, the truth is, is it isn't. It's ok, if your using other sites as well/doing internet searches, but apparently the minumum tank sizes and the adult sizes for some fish are incorect. Imo, out of the ones I linked to, age of aquariums is the best, but still, all 3 of them as well as web searches should be used to prove or disprove one sites information, to make sure what you know is actually the truth.
by the way, Ko Lo, your avatar is adorable. i love puffers and porcupinefish (both are in order Tetraodontiformes) for their smiles. my sister looks like a puffer because she has a perpetual half-smile on her face