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 copapods and amphipods, which are a staple food for certain fish and invertebrates kept in marine aquariums.
Purposes of Macroalgae
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 phosphate and nitrate from the water.
- Use moderate to high lighting and keep it in an area of high water flow.
Macroalgae Cultivated for Food (cont.)
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 (Sargassum echinocarpum)
- 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.
Nitrate (NO3) & Phosphate (PO4) Reducing Macroalgae
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.
- Chaetomorpha Algae (Spaghetti Algae)
- This algae is fast growing and is not palatable to many herbivorous species.
- 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 blades, notch leaf, and a grape-shaped variety.
Ornamental Macroalgae
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, rather than main tank.
Ornamental Macroalgae (cont)
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
- Must be pruned regularly to prevent rapid die-off during sexual reproduction which will polute tank).
- Can be found in various shapes, including flat blades, feather blades, notch leaf, and a grape-shaped variety.
Nutrients for Macroalgae
- Some aglae require phosphates and nitrates to survive.
- Some algae will not tolerate high nitrates of 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.
Sources for Amphipods
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.
