Snowflake Eel

I have been browsing around LiveAquaria lately and a came upon a snowflake eel in the diver's den. I have done a fair amount of research on them and I am considering getting one. I already have an extra power head, light, and substrate. What is the smallest size tank I could keep him in? Also, what type of filtration would I need I (I would like to keep the price as low as possible).