Cultivating Macroalgae in Your Saltwater Aquarium

Many saltwater aquarists cultivate certain species of macroalgae either in their main tanks, or in refugiums and sumps. Macroalgae is a major food source for a number of both fish and invertebrates in the oceans and many marine aquarists have found that growing their own macroalgae is a great way to feed their tank critters with an inexpensive natural food.

Macroalgae is sometimes called the "good kind of algae" as opposed to microalgae, (i.e. Hair Algae). Saltwater aquarists have found...MORE that a number of macroalgae species are very useful in their systems, providing food for the herbivores as well as reducing phosphates (PO4) and Nitrates (NO3) levels in their tanks. Some types of macroalgae also make excellent breeding grounds for copapods and amphipods, which are a staple food for certain fish and invertebrates kept in marine aquariums.

  • 01 of 08

    Purposes of Macroalgae

    Ulva fasciata
    Ulva fasciata. Photo by Keoki Stender


    Macroalgae cultivated in marine aquariums serves 3 different purposes: ornamental, nutrient (NO3, PO4) reduction and fish and invertebrate food.


    Macroalgae Cultivated for Fish Food

    • Kelp on Rock, Smooth Leaf (Haliptilon sp.)
      • Color can vary from a dark pink to deep red.
      • Does not tolerate high NO3 or PO4 levels
      • Does best in moderate to strong lighting.
      • Best when grown in a refugium, rather than main tank.
    • Lettuce Algae Ulva (U. fasciata, U. expansa)
      • Readily accepted by herbivorous fish.
      • Removes both...MORE phosphate and nitrate from the water.
      • Use moderate to high lighting and keep it in an area of high water flow.
  • 02 of 08

    Macroalgae Cultivated for Food (cont.)

    Red Algae (Gracilaria coronopifolia)
    Red Algae (Gracilaria coronopifolia). Photo by Keoki Stender
    • Limu Manauea (Gracilaria coronopifolia)
      • Endemic to Hawai'i.
      • Excellent surgeonfish food.
      • Remove ammonia, nitrates and phosphates from system water.
      • Does best in medium light.
      • Under the right conditions, biomass can increase 150% per month.
    • Prickly Sargassum (
      • Has short thick blades with prickly margins and spherical gas bladders.
      • Endemic to Hawaii.
      • Great surgeonfish food.
  • 03 of 08

    Nitrate (NO3) & Phosphate (PO4) Reducing Macroalgae

    Chaetomorpha antennina
    Chaetomorpha antennina. Photo by Keoki Stender
    • Shaving Brush Plant (Penicillus sp.)
      • Will benefit from the regular addition of an iron supplement, as well as trace elements.
      • Can go a long way towards helping reduce nitrate and phosphate from the water column.
    • Caulerpa
      • Must be pruned regularly to prevent rapid die-off during sexual reproduction which will pollute tank.
      • Can be found in various shapes, including flat blades, feather...MORE blades, notch leaf, and a grape-shaped variety.
  • 04 of 08

    Ornamental Macroalgae

    Halimeda kanaloana
    Halimeda kanaloana. Photo by Keoki Stender
    • Shaving Brush Plant (Penicillus sp.)
      • Will benefit from the regular addition of an iron supplement, as well as trace elements.
      • Can go a long way towards helping reduce nitrate and phosphate from the water column.
    • Halimeda Plant (Halimeda sp.)
      • Do not tolerate high NO3 or PO4.
      • Requires calcium.
      • Do not tolerate extensive pruning.
    • Kelp on Rock, Smooth Leaf (Haliptilon sp.)
      • Color can vary from a dark pink to deep red.
      • Low nutrient plant.
      • Does best in moderate to strong lighting.
      • Best when grown in a refugium,...MORE rather than main tank.
    Continue to 5 of 8 below.
  • 05 of 08

    Ornamental Macroalgae (cont)

    Caulerpella ambigua
    Caulerpella ambigua. Photo by Keoki Stender
    • Maiden's Hair Plant (Chlorodesmis sp.)
      • Good breeding ground for amphipods & copepods.
        • Contains a toxic substance which deters herbivorous fish from eating it.
    • Mermaid's Fan Plant (Udotea sp.)
      • Do not tolerate high NO3 or PO4.
      • Require calcium
    • Caulerpa
      • Can be found in various shapes, including flat blades, feather blades, notch leaf, and a grape-shaped variety.
      • Must be pruned regularly to prevent rapid die-off during sexual reproduction which will polute tank).
  • 06 of 08

    Nutrients for Macroalgae

      • Some aglae require phosphates and nitrates to survive.
      • Some algae will not tolerate high nitrates or phosphates.
      • Calcareous macroalgae (i.e. Halameda) require calcium supplements.
      • Some macroalgae (i.e. Shaving Brush Plant) benefit from the regular addition of an iron supplement, as well as trace elements.
  • 07 of 08

    Sources for Macroalgae

    Caulerpa webbiana
    Caulerpa webbiana. Photo by Keoki Stender
  • 08 of 08

    Sources for Amphipods

    Amphipod Image
    Amphipod. Photo by Stan Hauter

    Without a doubt, your best (and least expensive) way to obtain some amphipods and copepods to seed your refugium with is from a friend's tank or from a friendly LFS. Most copepods and amphipods that show up in a marine aquarium have hitchhiked in on live rock. They are easy to collect from a filter and transport to your tank very well.

    If you can not find amphipods or copepods locally, here are some which are commercially available.