When to Add Your First Fish

Before the first fish

Check the cycle is really done. See how to cycle a reef tank. Then do a water change to bring nitrate down, as Bulk Reef Supply suggests, and test again.

Which fish first

Bulk Reef Supply suggests one small, hardy fish, such as a small captive-bred clownfish. Pick something peaceful that suits your tank as an adult, and buy from a shop you trust.

Quarantine protects your display; see quarantine for marine fish.

How fast to add more

Bulk Reef Supply’s pace: one fish at a time, at least two weeks apart. Once two or three are established, several small fish can go in together, but larger fish still one at a time. Adding too many at once risks an ammonia spike that can wipe out the bacteria.

Test in between

Test ammonia and nitrite a few days after each new fish. If either reads above zero, hold off on the next fish until they’re back at zero.

How long after cycling can I add fish?

As soon as the cycle is confirmed and you’ve done a water change.

Can I add a clean-up crew first?

Many keepers add a small crew once the tank has cycled. Don’t add more than the tank can feed.

How many fish can I add at once?

Bulk Reef Supply suggests one at a time to begin with.