Top 10 Fish for a Nano Reef Under 50 Gallons
A nano reef is any reef tank under about 50 gallons, and it’s where a lot of people start. Small tanks are cheaper to light and easier to fit in a home, but they give fish less room to get away from each other and less water to soften mistakes. So the fish have to be small, peaceful enough to share close quarters, and happy to stay that way as adults.
After 18+ years of keeping and selling fish, these are the ten we recommend most for tanks under 50 gallons. Every one is reef safe (it leaves corals alone), and most are available captive-bred. Sizes are adult sizes, not the size you see in the store.
1. Ocellaris Clownfish
The Ocellaris Clownfish is the classic nano fish for a reason. Captive-bred clowns are tough, eat almost anything, and stay around 3 inches. A pair is fine in 20 gallons. They don’t need an anemone, and in a nano we’d usually skip one: anemones wander, and a small tank has few safe places for them. Keep one pair, added together, and only one kind of clownfish.
2. Yellow Watchman Goby
The Yellow Watchman Goby sits on the sand at the mouth of its burrow and watches the world go by. It reaches about 4 inches and suits 20 gallons and up. Pair it with a pistol shrimp and you get one of the best shows in the hobby: the shrimp digs, the goby stands guard. Give it a sand bed at least an inch or two deep.
3. Firefish Goby
The Firefish Goby and its cousin the Purple Firefish hover above a bolt-hole and flick their tall front fin. They’re peaceful, about 3 inches long, and beautiful under reef lights. They jump, so a nano with a firefish needs a lid or mesh screen. Keep one per tank unless you buy a mated pair.
4. Royal Gramma
Purple in front, yellow behind, and tougher than it looks, the Royal Gramma stays around 3 inches and likes 30 gallons or more. It claims a cave and hangs near it, sometimes upside down under a ledge, which is normal. Don’t keep two, and avoid other fish that look like it.
5. Tailspot Blenny
The Tailspot Blenny is our favorite blenny for small tanks. It’s small (under 3 inches), peaceful, picks at film algae between meals, and has more personality per inch than almost anything else in the hobby. It perches on rocks and pops in and out of holes all day.
6. Banggai Cardinalfish
The Banggai Cardinalfish is slow, calm and striking. It reaches about 3 inches and fits a 30 gallon tank. Wild Banggai are listed as endangered, so buy captive-bred ones; they’re hardier anyway. Keep one, or a pair you saw getting along. Larger groups often fight once they grow up.
7. Pajama Cardinalfish
The Pajama Cardinalfish has a yellow face, a polka-dot tail and big red eyes. It’s peaceful and easy to feed, and stays around 3.5 inches. In 30–40 gallons, a single fish or a small group of three works well.
8. Orchid Dottyback
Most dottybacks are bullies. The Orchid Dottyback is the gentle exception, and almost all of them are captive-bred. It’s a brilliant purple, about 3 inches long, and it eats bristle worms. Add it after your more timid fish so they get settled first.
9. Six-Line Wrasse
The Six-Line Wrasse is always moving, always hunting, and it eats pests like flatworms and small bristle worms. It stays around 3 inches. The caveat: as it settles in, it can get pushy, so add it last and skip it if you plan on very shy fish like firefish.
10. Bicolor Blenny
The Bicolor Blenny is half navy, half orange, and full of character. It grazes algae and takes frozen food. It grows to about 4 inches and suits 30 gallons and up. Most leave corals alone, but now and then one nips at large-polyp corals or clams, so watch it for the first few weeks.
Sample stocking for real tanks
These are starting points, not limits. Add fish one or two at a time, a few weeks apart, and quarantine them first.
- 20 gallons: a pair of ocellaris clownfish and a yellow watchman goby. Or a pair of clowns and a tailspot blenny.
- 30 gallons: a pair of clowns, a royal gramma and a firefish.
- 40 gallons: a pair of clowns, a yellow watchman goby with a pistol shrimp, a pajama cardinal and a tailspot blenny.
Fish to skip in a nano
- Tangs. Even the small ones, like the Yellow Tang, need 75 gallons or more to swim.
- Most damselfish. Small and cheap in the store, but many turn aggressive and are hard to catch later.
- Mandarin dragonets. The Mandarin Dragonet eats tiny live animals off the rock all day, and most nanos can’t grow enough of them. Only consider one in a mature tank, and only an individual you’ve seen eating frozen food.
- Lawnmower blennies. Great algae eaters, but they get big and often starve in a small tank once the algae runs out.
Where to go next
If you’re still setting up, read our guide to the best saltwater fish for beginners, and see what’s in stock today under beginner-friendly fish. Have a question about your own nano? Ask in the Support forum and our team will help you plan it.
