An aquarium is a closed system. As you feed your fish, waste builds up. Filtration and water changes help, but one of the best things you can do for a saltwater aquarium is hire a clean up crew (CUC for short). Whatever food your fish don’t digest becomes excess nutrients that fuel nuisance algae. That is why you see film algae on aquarium glass and green hair algae on rock. The CUC is a group of invertebrates that eat waste and algae, getting into all the small places a gravel vacuum misses.  Adding a CUC makes your aquarium more like a natural aquatic environment, eases maintenance, and adds to viewing enjoyment. If you have a reef tank, a CUC can help keep algae from aggravating coral. Want to get a crew working for you? Read on and learn about your options.  

When choosing a CUC, think of the three different zones of your saltwater fish tank: glass, sand, and rock. Invertebrates clean in different zones In addition, some invertebrates are herbivores that eat algae, while others are omnivores and detritivores that eat waste. Pick a mix that covers all your needs. 

Sand sifters

A lot of fish waste and uneaten food lands on the sand. Sand sifting invertebrates eat waste on and under the sand surface. Sand sifters also turn over the top layer of sand, which prevents dead spots where uneaten food can rot and anaerobic sand can build up. The sand is oxygenated as it is sifted, which improves the sand’s natural filtration ability.  

Algae eaters

Algae eaters, when used in combination, can tackle lots of different algae from the green hair algae and bubble algae that grow on rock to the film algae that also grows on the glass. Many snails take fine algae from the rocks and glass. Hermit crabs graze short hair and brush algae. Urchins eat virtually every algae including macroalgae and coralline algae, leaving rocks looking clean and new. Emerald crabs target bubble algae, aka valonia. 

Carnivores and Omnivores

Carnivores and omnivores eat a wide range of waste and algae. Hermit crabs, most of which also eat algae, are excellent aquarium janitors that comb the sand and rock for every morsel of food they can find. Nassarius snails are great at eating uneaten fish food, which if left will contribute to nitrate and phosphate in the tank. 

The clean up crew reduces waste and nutrients, so they do not increase your bioload or reduce the number of fish your fish tank can handle. Pick a variety of species to clean different areas and substances in your tank.  Do keep in mind that many aquarium invertebrates are sensitive to nitrates. So, if you have high nitrate issues you may want to do a series of water changes to lower the nitrates before adding the CUC, which will then help keep your nitrates low.  

Some of the most popular reef janitors are:

Cerith Snails - sand sifting omnivore

Fighting conch (Strombus spp.) - sand sifting omnivore

Nassarius Snails - sand sifting carnivore

Sand sifting starfish - Astropecten polyacanthus

Turbo snail - algae eater

Pyramid snail (Tectus spp.) - algae eater

Turban snail (Trochus spp.) - film algae eater

Hermit crabs - red leg and blue leg hermit crabs are versatile omnivores

Urchins - voracious algae eaters 

Emerald crab - Valonia bubble algae eating omnivore