The best replacement for sump is refugium.

The best alternatives to sump are rated as following:
★★★★★  refugium
★★★★  canister filter
★★  canister
★★  wet dry filter
★★  filter
★  no sump
★  external filter
★  canister saltwater
★  hob
★  dry sump
★  wet dry
★  submersible
★  skimmer
  wet sump
  draw straw
  hang on filter
  levin tube
  fx5
  canister filter saltwater
  rear sump
  wet\/dry
  refugium live rock
  bio balls
  van guard sump
  levine tube
  dobhoff tubes
  overhead filter

Your alternative for sump is not listed? Suggest!
Speaking about sump, one probably shouldn't forget about refugium.

Other search terms related to sump and their ratings are:
★★★★★ refugium
★★★★ skimmer
★★ canister filter
★★ built in skimmer
★★ protein skimmer
★ refugium and protein skimmer
★ overflow box
hob skimmer
built in protein skimmer
ato
You have in mind a companion for sump and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of sump in all years. Click on graph for more.
sump
refugium
canister filter