What to put in a aquarium/terrarium?
 

Hi all - I have a large (3ftx3ft) freshwater aquarium/terratium that I would like to add fish/etc to. It has about 20-25 gallons of aquarium space, with a wall made from porous terrarium cement holding off to one corner a 1.5ft x 2ft land area. Because the 'wall' is porous, I can't keep the water from turning a slight yellow/brown from the dirt in the terrarium, so I don't think picky fish would go well here. I would prefer fish that would stand out, even in the dimmer water. I also note that I am by far not a aquarium expert, and probably should have beginner fish.

My aquarium has a sandy bottom currently, though I can change to pebble. It will have live plants and wood branches for hiding. I would like to have as much diversity as possible, with fish, shrimp, snails - even an amphibian (frog? newt?) if I can pull it of. But I have no idea what would get along with what! I am also not flowing with cash, so $15+ per fish is a no-can-do.

Hope you can help - thanks all!