ok...i just upgraded my 55 w/ 20L sump to a 75 w/ 55 sump. the 75 i have made into a coral + fish. you all now how we are with our hobby. i now have to find something to do with my 20L. i'm not to into the idea of starting another reef up, but are there any other aggressive fish that would be able to live in the 20g setup happy. i would really like a dwarf lion, but am not sure on the size tank needed for it. i have also considered certain eels that do not get to large. thank you for your time.