With a 90 gallon tank you have so many options. If you want it planted it would rule out an oscar. Lol. You could do anything from large schools of nano fish, a betta community, dwarf chichlids to larger fish.
Thanks friends. I know that we can’t really have any cool water species. Our house doesn’t ever really go below 25 degrees celsius. My son really wanted hillstream loaches in this tank, but I think it would be too warm for them. We are also looking for species outside of livebearers, we have a few of those already in another tank.
We also have another tank that is 29 gallons. The plan for that tank is a pair of German Blue Rams, a school of Corydoras Sterbai, a school of Cardinal Tetras and a school of Cherry Barbs. So hoping for different species than the ones we already have or are planning to have.
Rams are always great and would likely carry the high potential to live a long time in such a large tank. Maybe not hillstream loaches, as cool as they look, those species of loaches require a strong water current, especially in a big tank, which if you opt to choose 'em, may require 1-2 very strong PH's and/or circulators.
Or you could do one larger puffer, I don't think its big enough for a mbu but there is probably a freshwater puffer just right. You could also try just one of a really aggressive cichlid like a flowerhorn. Maybe you could do oscars. Maybe a buttikoferi tilapia, i hear those are one of the most aggressive cichlids.
I don't even know what to say! There are so many options!! I like goldfish, Angels, discus, you could have LOTS of colourful guppies!! A blood parrot chiclid? I love those but I don't know if they can be in a 90, I bet they can though! Petsmart says a 29 gallon so I'm sure the minimum is around there