Senegals are a good Birchir to start with. They are very common now(they even sell them at petsmart, they call them dinosaur eels) and they are the cheapest Birchir $5-10 . They come in regular color (brown,grey,or beige) and Albino. They stay small which would be good for your tank. But make no mistake, they are predators and will happily eat any fish they can fit in their mouth. I've attached some pics of my Senegals for you. Ones an albino and one regular. They are about 6" now about half grown.