well i have a 2.8 gallon plastic comntainer which is pretty bigger than a glass tank of 2.8 gallons. and i have 2 guppys, 1 goldfish and 1 crayfish. you know everything really depends on the filteration u have and the maintence u go through. i happen to be going it smooth. so for all the sake u could get tetras, guramis,crayfish,shrimp, guppys(especially), and bettas.