I think your tank is consider nano tank. You should keep peaceful and small fishes. Use small rocks to create small caves and gives more space for fishes to swim.
About your sump, you should get the advice from your tank maker.
I have 2 sets of the above for sale. All blue led.
Bought less than 1 month ago.
Stll have more than 11 months waranty.
Each set is for a 2 ft tank.
Link to the light set.
http://www.madpetz.c...products_id=680
Bought at $170 each.
Willing to hear to reasonable offer.
PM to deal at Bukit Batok.