The onyx clownfish is a percula with black filling the body between broad white bars, and you buy it for what it becomes. It is hardy, mostly peaceful and easy to keep in the middle of a reef tank.
Did you know
The onyx clownfish's black is not present at hatching. The dark flanks are pigment spreading between the bars as the fish matures, so a shop tank of young onyx can disappoint.
Caring for the onyx clownfish
Give an onyx clownfish a tank of at least 20 gal (75 L). Captive-bred fish adapt well to reef aquariums, and the species is reef safe.
Keep the water at 75 to 82°F (24 to 28°C), with a pH of 8.1 to 8.4. Captive-bred onyx clownfish readily accept flake, pellet and frozen foods.
The onyx clownfish is peaceful toward other species and fits a community tank. It will still defend its host and territory against other clownfish, so keep it alone or as a bonded pair.
A mated pair is a dominant female and a smaller male. Like all clownfish, it is a protandrous hermaphrodite, and the male will change sex if the female is lost. Breeding onyx clownfish is easy.
Good to know
The onyx clownfish is sold as Onyx or Onyx True Percula. Perculas in general darken with age, but onyx stock carries the trait much further.
In the wild
The onyx clownfish sits in the pedigree of the designer perculas. ORA founded its Picasso line in 2004 by pairing a wild Solomon Islands male with a typical onyx female. The two families share a root.
Symbiotic relationships
Clownfish and their host anemones
A clownfish lives inside an anemone that stings and eats other fish its size. Its mucus coat keeps the anemone's stinging cells from firing, and a new fish builds that protection up over hours of brief touches. The fish gets a refuge no predator will follow it into and a nest site at the anemone's base. The anemone gets a guard that drives off the butterflyfish that would graze its tentacles, a steady supply of nitrogen from the fish's waste, and water movement at night, when the fish fans its fins among the tentacles and the anemone takes up more oxygen. Only ten anemone species host clownfish in the wild, and each clownfish species uses its own short list of them.
Captive-bred clownfish have never seen an anemone and do not need one; they settle for a coral, a powerhead or a corner of the tank. If you want the pairing, the anemone is the harder animal by far and goes in first, into a mature tank with strong light and stable water, at the tank size its own profile lists. The bubble tip anemone is the hardy host, and the one most clownfish accept in captivity even when it is not a natural host, so a clownfish profile lists it as the usual tank host where that is the case. The sebae, magnificent and carpet anemones are marked difficult, and the carpets eat fish. Expect a paired clownfish to defend its anemone against everything else in the tank.
The onyx clownfish is a mostly peaceful, social species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.
Is an onyx clownfish a different species from the Percula clownfish?
No. An onyx clownfish is a variety of the Percula clownfish, Amphiprion percula, and it wants the same tank, water and food as the species.
Is the Onyx clownfish a wild form?
Closer to one than most designer perculas. The onyx look comes from wild percula populations around Papua New Guinea where dark-bodied fish occur naturally, and hatcheries built captive lines from that broodstock. What farms select for is how completely and how early the black fills in.
When does an Onyx clownfish turn black?
Over months. Juveniles ship looking much like a normal percula and the flanks darken with age, ending near solid black between the bars. Coverage varies between suppliers and siblings, so ask for a photo of adult stock from the same line.
What size tank does an onyx clownfish need?
An onyx clownfish needs at least 20 gal (75 L). It spends most of its time in the middle.
What does an onyx clownfish eat?
An onyx clownfish readily accepts flake, pellet and frozen foods.
How big does an onyx clownfish get?
An adult onyx clownfish reaches about 3.1 in (8 cm).
How can you tell a male onyx clownfish from a female?
Males are the smaller fish of a pair. The dominant onyx clownfish is the female, and the male will change sex if she is lost.
How does an onyx clownfish breed?
Onyx clownfish breed as a mated pair, a dominant female with a smaller male. Breeding them is easy.
3.1 in (8 cm)20 gal (75 L)75–82°F (24–28°C)
3.5 in (9 cm)30 gal (115 L)75–81°F (24–27°C)
3.9 in (10 cm)30 gal (115 L)75–82°F (24–28°C)
4.3 in (11 cm)26 gal (100 L)75–82°F (24–28°C)
4.7 in (12 cm)30 gal (115 L)75–82°F (24–28°C)
5.1 in (13 cm)40 gal (150 L)75–82°F (24–28°C)