You said you are using a 20 gallon aquarium. I was just saying that most folks who keep pumilio recommend a minimum of a 20 gallon aquarium, usually bigger. Pumilio enjoy their space.
I've heard that. The 20g is almost finished and I've got a 29g started, and a 50gal long available. Once both of my female Cobalts are gone, I'm going to redo the 80 hex.
I can always move 'em if they start complaining...