The best replacement for refugium is sump.

The best alternatives to refugium are rated as following:
★★★★★  sump
★★★★  wet dry
★★★★  biopellets
★★★★  skimmer
★★★  bio balls
★★★  no refugium
★★★  algae scrubber
★★★  protein skimmer
★★★  reactor
★★  canister filter
★  wet dry filter
★  berlin
★  algae turf scrubber
★  berlin sump
★  dsb
★  ats
★  gfo
★  carbon dosing
★  wet\/dry
  sump filter
  trickle filter
  live rock
  sump tank
  live rock in sump
  phosphate reactor
  saltwater refugium
  wet\/dry filter
  sump saltwater

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

Other search terms related to refugium and their ratings are:
★★★★★ protein skimmer
★★ canister filter
★ skimmer
★ bio balls
★ biopellets
★ freshwater
wet dry filter
trickle filter
sump
red sea max
You have in mind a companion for refugium and it is not yet here? Propose!



Google Trends

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refugium
sump
wet dry