What Eats Macroalgae? The Best & Worst Tankmates.

Macroalgae play a crucial role in reef and saltwater aquariums, helping with nutrient export, providing habitat for microfauna, and enhancing the aesthetics of a tank. But if you’re adding macroalgae to your system, one important question to ask is: What eats macroalgae?

Some tank inhabitants will happily snack on or completely devour your macroalgae, while others will leave it untouched. In this guide, we’ll cover the best and worst tank mates for keeping macroalgae in your saltwater aquarium.

Best Tank Mates for Macroalgae

If you want to grow macroalgae successfully, you’ll need to choose tank mates that will either ignore it or benefit from its presence without destroying it. Here are some ideal companions:

1. Copepods and Amphipods

- These tiny crustaceans thrive in macroalgae, using it for shelter and a food source.

- A well-established macroalgae patch can boost pod populations, which in turn serve as food for fish and corals.

2. Seahorses and Pipefish

- These delicate fish love hunting copepods and amphipods that live in macroalgae.

- They don’t eat macroalgae directly, making them excellent tank mates.

3. Clownfish, Gobies, and Blennies

- Most of these small fish species won’t touch macroalgae.

- Some blennies (like the Lawnmower Blenny) eat nuisance algae but typically ignore structured macroalgae like Chaeto.

4. Soft Corals and LPS Corals

- Corals and macroalgae can coexist as long as they aren’t competing for space or light.

- Soft corals like Xenia and some LPS corals can benefit from the improved water quality macroalgae provides.

5. Snails and Non-Algae-Eating Crabs

- Species like Cerith, Nerite, and Nassarius snails will clean up detritus without harming your macroalgae.

- Scarlet Reef Hermit Crabs and some small reef-safe crabs won’t damage macroalgae but help with general tank maintenance.

Worst Tank Mates for Macroalgae

Certain fish and invertebrates will make quick work of your macroalgae, either eating it directly or uprooting it. If you want to keep macroalgae, it’s best to avoid these species:

1. Tangs and Surgeonfish

- Herbivorous fish like Yellow Tangs and Kole Tangs love eating algae—including macroalgae.

- If macroalgae is your primary nutrient export method, these fish can quickly deplete it.

2. Rabbitfish and Foxface

- These fish are excellent at controlling nuisance algae, but they won’t distinguish between pest algae and your prized macroalgae.

3. Urchins

- Sea urchins are notorious for bulldozing through rockwork and eating macroalgae, especially species like Chaetomorpha and Gracilaria.

4. Large Hermit Crabs

- While small reef-safe hermits are fine, larger species (like the Halloween Hermit Crab) can be destructive.

- They may pull apart macroalgae while foraging for food.

5. Some Wrasses and Parrotfish

- While most wrasses are reef-safe, certain species may nibble on macroalgae or disrupt it while hunting for small invertebrates.

- Parrotfish, which aren’t common in home aquariums, will eat macroalgae if given the chance.

How to Protect Your Macroalgae

If you already have herbivorous fish or invertebrates in your tank, but still want to keep macroalgae, here are a few solutions:

-Use a Refugium : A dedicated refugium keeps macroalgae separate from main tank inhabitants, allowing it to grow undisturbed.

- Secure Macroalgae in Hard-to-Reach Areas : Placing macroalgae in high-flow areas or tucked into crevices may prevent some fish from reaching it.

- Choose Hardy Macroalgae : Species like Caulerpa and some Gracilaria varieties may be more resilient against occasional grazing.

- Feed Herbivorous Fish Well : Providing plenty of nori (dried seaweed) and algae-based foods can reduce their interest in live macroalgae.