I'm sorry but no turtle can live in a 2.5 gallon tank. You will need a least a 20 gallon tank and that is even iffy when they grow up I would say get a 30-40 gallon tank for one turtle.
About a 20 gallon tank.
I think it depends on how big the turtles are.
Neons
for two males a ten gallon tank heavly planted, two females 1 gallon, male and female same as first one
Depending on the species, one or two. Turtles will keep growing through their entire lives, overcrowding or expecting them to only grow to the size of the tank is something that usually leads to dead turtles.
10 gallon
Eastern Box Turtles Live in Swampy Places eastern box turtles live in open feilds associated with marsh
depends, can a ten gallon tank live in a goldfish
No shark can live in a 3 gallon tank. It would be a nice home for a Betta though!
no.you have to have at least an 90 gallon tank or an 100 gallon tank.
I would suggest upgrading to a 10 gallon tank.
10 gallon tanks can fit some snakes and you they can also fit geckos. I have a gopher snake in a 10 gallon and it fits with a good amount of space for a big hide.