How big of a sump do I need for a 55g planted tank (48L 13W 28H) I was thinking about having it as a sump/ refugium. I'm planing on using duckweed in the refugium. I read in Tropical Fish Magazine that duckweed can remove nitrogen, phosphors, potassium. magnesium, calcium, sodium, chlorine, boron, iron, sucrose, fructose, glucose, urea, and most amino acids... So here is the next question what other media do I need. do I use bio balls or sponge or any thing... Question # 3 what size pump do I need. The top of tank will probably be about 6ft off of the ground.... This is my frist time making a sump any information will help...