Key takeaways
- Invertebrates such as shrimp, snails, hermit crabs, starfish and urchins make up a reef tank's clean-up crew. They also add colour and interesting behaviour.
- Most invertebrates are very sensitive to salinity swings and copper. Drip acclimate them, and never use copper-based medications in a tank with inverts.
- Add inverts once your tank is cycled and stable, and build your clean-up crew gradually.
- Check reef compatibility before buying. Some crabs, urchins and starfish can damage corals or small livestock.
Invertebrates are the unsung heroes of a reef aquarium. They graze algae, scavenge leftover food, sift sand and add colour and personality to your tank. This guide covers popular reef invertebrates and how to look after them. It also explains how to build a balanced clean-up crew.
Popular reef invertebrates
| Group | Examples | Role in the tank | Reef safe? |
|---|---|---|---|
| Shrimp | Cleaner shrimp, fire shrimp, peppermint shrimp | Scavenging; cleaning fish; peppermints may eat aiptasia | Generally yes |
| Snails | Turbo, trochus, cerith, nassarius | Algae grazing; sand-bed stirring | Yes |
| Hermit crabs | Small reef hermits | Scavenging and algae eating | Mostly; may compete with snails for shells |
| Starfish | Sand-sifting stars, brittle stars | Sand sifting and scavenging | Depends on species; research first |
| Urchins | Tuxedo urchin and others | Excellent algae grazing | Usually; may knock over loose corals |
| Clams and anemones | Tridacna clams, bubble tip anemones | Display animals | Need strong light and stable water; anemones can move |
Learn more about one of the most popular reef inverts in our cleaner shrimp care guide.
Water requirements
Invertebrates need stable conditions and are often less tolerant than fish:
- Salinity: steady at about 35 ppt (SG 1.025–1.026). Avoid sudden changes.
- Temperature: 25–26 °C.
- Ammonia and nitrite: zero. Keep nitrate low.
- Iodine and magnesium: shrimp and crabs use these when moulting, and regular water changes help maintain them.
- No copper: copper medications and some plant fertilisers are toxic to invertebrates.
See our water chemistry guide for target ranges and testing tips.
Acclimating invertebrates
Use a slow drip acclimation over about 45–90 minutes, keeping the animal submerged the whole time. Exposure to air can harm sponges, starfish and clams. Our acclimation guide walks through the drip method step by step.
Building a clean-up crew
- Start small, with a few snails and hermits, and add more if algae remains. Too many grazers will starve.
- Mix species: snails for glass and rock, nassarius or cerith for the sand bed, and shrimp for leftover food.
- Provide spare empty shells for hermit crabs so they don't attack snails.
- Feed scavengers lightly if the tank is very clean.
Moulting: what's normal
Shrimp and crabs shed their exoskeleton as they grow. An empty shell that looks like a whole shrimp is usually just a moult. Your shrimp will hide for a day or two while its new shell hardens. Leave the moult in the tank, as other animals will eat it and recycle the minerals.
Common mistakes
- Adding inverts to an uncycled tank.
- Rushing acclimation, as salinity shock is a leading cause of invert losses.
- Keeping inverts with predatory fish such as triggerfish, puffers or some wrasses.
- Using copper treatments in the display tank.
- Buying sand-sifting stars for a small or new tank without enough natural food.
Shop reef invertebrates
Browse our invertebrates, shrimp, starfish and snails and anemones, quarantined in-house and shipped NZ-wide. Check the shipping information page for delivery options.
Frequently asked questions
What is the best clean-up crew for a reef tank?
A mix of algae-grazing snails, sand-sifting snails, a few small hermit crabs and a cleaner or peppermint shrimp suits most reef tanks. Scale numbers to your tank size and algae level.
Why did my shrimp die after adding it?
The most common causes are a rapid salinity change during acclimation, copper exposure or an unstable new tank. Always drip acclimate slowly.
Are starfish reef safe?
Some species are reef safe, but others, such as some sea stars, may eat corals or clams. Research the exact species before you buy.
