In a 36 gallon ... you can easily keep 12 TigerBarbs, even a few more.... they are very active and get about 2-3 inches at most. If you do 12, I'd recommend 4 each of the regular, albino and Green TigerBarbs ... they would offer a nice color combination. Since they're just color variations of the same species, they'll shoal well together.
I don't think they poop any more than other fish ... but they are voracious eaters .. so they'll poop their fair share.
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.