Building a healthy reef tank isn’t just about corals and fish—the unsung heroes are your clean up crew. These snails, crabs, shrimp, and other invertebrates quietly handle algae, leftover food, and detritus so your display stays stable and beautiful. In this clean up crew guide, we’ll walk through what they do, how many you actually need, and how to choose the right mix for your aquarium.

What Is a Clean Up Crew and Why Do You Need One?

Your clean up crew (often called CUC) is the team of invertebrates that help maintain water quality and tank cleanliness. They don’t replace regular maintenance, but they make it easier and more effective.

Main Jobs of a Clean Up Crew

• Algae control: Many snails and some crabs graze on film algae, hair algae, and diatoms.
• Detritus removal: Hermit crabs, nassarius snails, and certain shrimp eat leftover food and waste.
• Sand bed turnover: Sand-sifting snails and stars keep your substrate oxygenated and cleaner.
• Preventing nutrient spikes: By consuming leftovers, they help keep nitrate and phosphate in check.

Tip: A clean up crew works best when paired with good export methods. If you’re still dialing in nutrient control, check out our guide on choosing and tuning a protein skimmer.

Choosing the Right Clean Up Crew for Your Tank

There’s no one-size-fits-all recipe. The best mix depends on tank size, rockwork, sand bed, and what kind of algae or waste you’re dealing with.

Core Clean Up Crew Members

• Trochus and Astrea snails: Excellent for film and light hair algae on rock and glass. Trochus can flip themselves if they fall.
• Nassarius snails: Great in sand beds. They eat leftover food and help prevent dead spots.
• Cerith snails: Versatile grazers that work on rock, glass, and sand, especially after lights out.
• Hermit crabs (scarlet, blue-leg): Active scavengers; helpful, but can occasionally bother snails for shells.
• Cleaner or peppermint shrimp: Shrimp add personality and help with leftover food; peppermint shrimp may help with certain pests.

How Many Clean Up Crew Members Do You Need?

Old rules like “one snail per gallon” are usually excessive. A more realistic starting point for a new or moderately stocked tank is:

• 10–15 snails for a 20–30 gallon tank, mixed species.
• 20–30 snails for a 40–60 gallon tank.
• 1–5 hermits per 20 gallons, depending on your preference.

Start small, then add more as you see how quickly they handle algae and waste. Overloading the tank with a huge crew often leads to starvation later.

Tip: If your rocks are spotless and snails rarely have visible algae to graze, your crew may be oversized. Consider rehoming a few or simply stop adding more.

Care, Compatibility, and Long-Term Success

Clean up crew members are hardy, but they still need stable conditions. Sudden swings in salinity, temperature, or alkalinity can wipe out sensitive inverts.

• Acclimate slowly: Use a drip acclimation method for 30–60 minutes when adding new inverts.
• Provide extra shells: If you keep hermits, add a variety of empty shells to reduce aggression toward snails.
• Feed lightly: A good crew helps you run a lower-waste system, but you still need to avoid overfeeding.
• Watch fish compatibility: Some wrasses, puffers, and larger crabs may eat snails and shrimp.

As your tank matures, your clean up crew needs will change. Early on, diatoms and film algae may call for more snails, while a mature reef with stable nutrients may only need a modest maintenance crew. Pair your CUC with strong basics—good flow, regular water changes, and a solid reef tank maintenance schedule—and you’ll find the balance that keeps your system thriving.

In the end, a thoughtful clean up crew is one of the easiest and most natural tools you have for keeping your aquarium stable. Choose species with a purpose, stock them gradually, and adjust over time. Your corals, fish, and your future self doing less scraping and siphoning will thank you. For more stocking ideas beyond inverts, visit our beginner reef fish guide and build a peaceful, efficient ecosystem from the ground up.