Ocular coralblenny

Where they come from

Ocular coralblennies (Ecsenius oculatus) are little reef perchers from the Indo-Pacific. You will usually find them on rocky reef slopes and coral rubble where there is plenty of film algae to graze and lots of tiny holes to duck into.

They are one of those fish that spend half their day posted up like a lookout, then suddenly hop to the next rock like a spring-loaded toy.

Setting up their tank

Give this fish rockwork with real nooks and crannies. They do not want open water. Mine picked a favorite bolt-hole within the first hour and basically treated it like home base.

Tank size is less about gallons and more about territory. A single ocular coralblenny does fine in a typical nano or larger reef as long as you have stable water and enough rock surface to graze. If you pack the tank with other perchers (other blennies, some gobies), you will see more squabbling.

• Rockwork: lots of small caves, cracks, and overhangs. Think "maze," not "pile."
• Flow: moderate is great. They like to sit in the breeze but still need calm spots to rest.
• Lighting: whatever your reef uses. Stronger light grows more film algae, which they appreciate.
• Cover: use a lid or mesh top. They can jump, especially during new-tank jitters.

What to feed them

Most Ecsenius blennies are big on grazing, and ocular coralblennies are no exception. They pick at film algae, diatoms, and the tiny bits living in it. In a squeaky-clean tank with bare rock, they can look fine at first and then slowly get skinny.

• Daily base: dried nori or other seaweed (small strip on a clip, or rubber-banded to a rock).
• Pellets/flakes: a quality herbivore pellet or spirulina flake works well once they recognize it as food.
• Frozen: mysis and brine are fine as a treat, but do not make it the whole diet.
• Real reef snacks: letting some film algae grow on a couple rocks is honestly one of the best "foods" you can provide.

How they behave and who they get along with

They are personable, alert fish. Mine would track me across the room and pop out the second I walked up to the glass. They are not aggressive in the "hunt you down" way, but they can be stubborn about their chosen hole.

They usually do fine in a community reef with peaceful fish. Trouble starts when you put them with other fish that want the same perches and caves, or with fish that harass anything that sits still.

• Good tankmates: most peaceful gobies, dartfish, clowns (in reasonable tanks), wrasses that are not bullies, reef-safe inverts.
• Use caution: other blennies (especially similar-shaped ones), hawkfish that may pester them, territorial damsels in smaller tanks.
• Avoid: aggressive dottybacks, big mean wrasses, and anything that has a habit of biting fins.

Breeding tips

They are cave spawners. In a settled tank you might see courtship and a pair sharing a hole, with the male guarding eggs stuck to the rock inside. Getting the eggs is the easy part. Raising the larvae is the hard part.

If you want to try, you will need a separate larval setup and live foods (rotifers first, then copepods/Artemia as they grow). The larvae are tiny and go into the water column fast, so overflows and powerheads become death traps.

• Give them spawning sites: small caves, short lengths of PVC tucked into rock, or tight crevices.
• Keep the pair well-fed on algae-forward foods so they have energy to spawn.
• If you see egg-guarding, reduce nighttime surprises: stable lighting schedule and no sudden tank re-scapes.
• For larval attempts, plan for live food cultures before you ever see eggs.

Common problems to watch for

Most issues I see with these blennies come down to food and stress. They can look totally fine while slowly losing weight, especially if the tank is too clean or if faster fish steal everything you add.

• Slow starvation: pinched belly, constant grazing, fading energy. Fix with more algae foods and some natural film algae growth.
• Being outcompeted at feeding time: they are not speed-eaters. Target-feed near their rock or drop food in multiple spots.
• Jumping: especially in the first week or after a scuffle. A lid saves lives.
• Ich/velvet risk: like most marine fish, they can get hit hard if stressed. Quarantine helps a lot.
• Territory spats: torn fins or hiding all day if they share the tank with another blenny or a pushy perch fish.

If you set them up with plenty of rock, let a little algae exist, and feed like you mean it, they are fantastic little characters. They are the kind of fish you notice all day long, even if they never leave their favorite rock.