The best replacement for skimmer is refugium.

The best alternatives to skimmer are rated as following:
★★★★★  refugium
★★★  main drain
★★★  no skimmer
★★★  canister filter
★  overflow pool
★  algae scrubber
★  overflow
★  chaeto
  uv sterilizer
  purigen
  reactor
  power filter
  fuge
  swc cone skimmer
  protein skimmer
  reef octopus
  surface skimmer
  prizm skimmer
  sump

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

Other search terms related to skimmer and their ratings are:
★★★★★ sump
★★★★ refugium
★★★★ miracle mud
★★★ filter
★★★ canister filter
★★ sump？
You have in mind a companion for skimmer and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of skimmer in all years. Click on graph for more.
skimmer
refugium
main drain