The best replacement for fish farming is fish ranching.

The best alternatives to fish farming are rated as following:
★★★★★  fish ranching
★★  aquaculture
★  pisciculture
  ranching

Your alternative for fish farming is not listed? Suggest!
Speaking about fish farming, one probably shouldn't forget about hydroponics.

Other search terms related to fish farming and their ratings are:
★★★★★ hydroponics
You have in mind a companion for fish farming and it is not yet here? Propose!



Google Trends

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fish farming
fish ranching
aquaculture