caulerpa macro to remove nitrates and phosphates from a saltwater aquarium

4 types of macroalgae that can help keep your phosphates and nitrates down

Here are 4 types of macroalgae that can help get your phosphates and nitrates down:


halimeda macroalgae

Halimeda is a macroalgae that you can actually use as a decorative plant. It is generally hardy in a saltwater tank, growing well under most aquarium conditions. It is relatively hungry for light (thriving under moderate to strong levels of light). One thing that makes this macroalgae interesting (could be considered a downside by some) is that it absorbs calcium from the water and includes it into its tissue, similar to coralline algae.

It is relatively easy to prune, is not invasive and won’t be eaten by most aquarium inhabitants.


Chaetomorpha is a thin, spaghetti-like macroalgae that grows quickly in a saltwater aquarium. Very quickly. Give it moderate-to-high lighting and good water flow and it will do a great job of removing nitrates and phosphates from your aquarium water. It grows densely in clumps that also serve as a good home for copepods and other invertebrates like mysis shrimp.

chaetomorpha macroalgae


Caulerpa is a macroalgae that you either love or hate. Love it, because it is extremely tolerant of even less-than-perfect aquarium conditions and grows…well…like a weed. Hate it because it grows…like a weed and is hard to get rid of…like a weed.

caulerpa macroalgae
This is a picture of a fern Caulerpa macro algae available at one of the local fish stores in my area


Another great saltwater aquarium macroalgae that can help keep your phosphates and nitrates down is called Ulva, or sea lettuce. Alva is a fast-growing, hardy macro that will grow well in most tanks…that is…until it gets eaten by your tangs…which is another great reason to try and grow these algae in your tank. According to some sites, it removes phosphates and nitrates from the water.

Sea lettuce or ulva macro algaeWhere to grow your macroalgae?

If you like the look of it, you could grow the macroalgae in your display tank. If you want to lower phosphates and nitrates without having to look at the macro, then the best place to grow it would be in your sump or refugium.

Macroalgae for sale

If your local fish store doesn’t have a nice selection of macroalgae, you can get some online at LiveAquaria or even eBay






2 responses to “4 types of macroalgae that can help keep your phosphates and nitrates down”

  1. Vivian

    Plants having a difficult time in 175 gal. Too deep, not enough light? outer 1/3 of leaves are clear like glass. Grow great in 17 gal. Do I need more co2?

    1. Hi Vivian, thanks for the comment/question. Adding CO2 would lower the pH of your system, so let’s try to rule some other things out, first. Are your corals in similar positions in the tank growing well/fine at those same relative positions (when compared with light source/quality?) Do you have Macro that is growing higher up (closer to the lights) that is thriving more? Is there a lot more competition for nutrients in the big tank? How are the water parameters similar or different between the two tanks? Any differences in Mg, Ca, ALK?

Leave a Reply

Your email address will not be published. Required fields are marked *