An Animal that can fit in such a space?

[nazanova]

So I've decided with my mum that when the fish pass we wouldn't like the tank or space go to waste so we'd like a new, more interesting animal to go there. We can change the tank to an exo terra if need be but we can't really change the space so I thought I'd ask you guys for some possible ideas if any that can be housed in such spaces, they can be any type of animal as long as they aren't that expensive or too hard to care for. We have thought about arboreal snakes but most are quite expensive and they would need a much larger space, we've thought about a Hognose so that's on our list as they are very small and don't need a large amount of space. We have considered frogs but they aren't very appealing to us, nor would they make a good "display" in our opinion. We would LOVE a Beardie or a Chameleon but obviously they cannot be housed in such a tiny space, so any ideas guys? (Ignore the dirty tank these pictures were taken before we cleaned it out)