I would definitely not advise keeping a GT in a 55 for life unless its female. I had a 8.5" GT in a 72 and felt bad for it. Not to mention if its a glass banger it could easily hurt itself in a 55 if it flips out.
Firemouth is a much better option. You might also want to check out rainbow wolf fish and possibly even a gulper cat.
If you do a DIY sump, find a way to cover the walls of the stand with soundproof material, because the water noise might drive you crazy. I don't mind it so much anymore, but yeah...
Doing a DIY sump is a lot easier than it sounds, and the pump really is the most expensive thing. You can get a good one for a 55 for around 70 bucks.
Now those exodons are something. Like mini piranhas. Ill look into those. I wass just at the store checkin out the tanks. Standard dimensions with a basic hood. Anyone have experience with pet supermarket aquariums
Mini piranhas for sure! Also theyre good looking little guys, but fierce as hell. Not a lot of guys on here do them, so it would also be pretty unique. You'll never have to even consider a bigger tank for them either. And by the looks of most exo vids, given proper filtration you could bump it up from 12-15 to 20+ individuals.