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 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 copepods and amphipods, which are a staple food for certain fish and invertebrates kept in marine aquariums.

  • 01 of 07

    Purposes of Macroalgae

    Macroalgae
    Flickr CC 2.0

    Macroalgae cultivated in marine aquariums serve 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 the main tank.
    • Lettuce Algae Ulva (U. fasciata, U. expansa)
      • Readily accepted by herbivorous fish.
      • Removes both phosphate and nitrate from the water.
      • Use moderate to high lighting and keep it in an area of high water flow.
  • 02 of 07

    Macroalgae Cultivated for Food (cont.)

    Translucent red algae
    DeborahMaxemow / Getty Images
    • 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.
    • Feathery Caulerpa (Caulerpa sertularoides)
      • Does best in medium light
      • Likes strong to medium current.
      • Great surgeonfish food.
  • 03 of 07

    Nitrate (NO3) & Phosphate (PO4) Reducing Macroalgae

    Caulerpa Seaweed, Caulerpa sp., Susac, Dalmatia, Adriatic Sea, Croatia
    Borut Furlan / Getty Images
    • 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 the tank.
      • Can be found in various shapes, including flat blades, feather blades, notch leaf, and a grape-shaped variety.
  • 04 of 07

    Ornamental Macroalgae

    Halimeda Ghost Pipefish
    Borut Furlan / Getty Images
    • 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, rather than the main tank.
    Continue to 5 of 7 below.
  • 05 of 07

    Ornamental Macroalgae (cont)

    Fresh caulerpa lentillifera (umi budo) in hands
    Ippei Naoi / Getty Images
    • 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 pollute tank).
  • 06 of 07

    Nutrients for Macroalgae

    Full Frame Shot Algae In Lake
    Moritz Haisch / EyeEm / Getty Images
      • Some algae 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 07

    Sources for Amphipods

    Amphipod Image
    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.