Reticulate clingfish

Where they come from

Reticulate clingfish (Tomicodon lavettsmithi) are tiny shore-hugging fish from the tropical western Atlantic, showing up around rocky coastlines and reef rubble where there is surge and lots of little hiding spots. They live their whole life glued to hard surfaces with that suction-cup belly, picking at micro-life you barely notice.

In the hobby they are one of those "blink and you miss it" fish. Super cool if you like cryptic, behavior-focused tanks, but they are not a showy swimmer in the open.

Setting up their tank

Think small, stable, and structured. I have had the best results treating them like a micro-predator that wants a wall of texture, not a big open reef. They spend most of their time on rock faces, under ledges, and in tight crevices.

• Tank size: 10-20 gallons works if it is mature and you keep nutrients in check. Bigger is fine, but don't assume bigger fixes husbandry issues.
• Mature biofilm: aim for an established tank with pods and "life" on the rock. Brand-new sterile rock makes them harder to keep feeding.
• Rockwork: lots of vertical faces and overhangs. I like a few fist-sized rubble piles too.
• Flow: moderate, varied flow. They handle surge-y conditions, but avoid blasting their favorite perch with a powerhead nozzle.
• Cover: use a lid. They are clingfish, but startled fish do weird things.
• Parameters: keep reef-like salinity (around 1.025), stable temp, and low swings day to day. Stability matters more than chasing a magic number.

What to feed them

This is the make-or-break part. Most clingfish do not act like normal "reef fish" at feeding time. They will not necessarily rush into the water column for pellets. Mine did best with small meaty foods delivered right to their perch.

• Start with live or moving foods if the fish is new or shy: live copepods, enriched baby brine, small live mysis if you can source it.
• Frozen usually works once they settle: cyclops, calanus, finely chopped mysis, roe/eggs, chopped clam or shrimp.
• Prepared options: tiny sinking carnivore pellets can work for some individuals, but I would not count on it at first.
• Feeding style: target feed with a pipette or turkey baster. Put the food right in front of the fish, then back off.

Frequency matters. They are small, and a lot of them do better with small meals more often rather than one big dump of food. I would rather feed lightly 1-2 times a day than overfeed and foul the tank.

How they behave and who they get along with

They are calm, cryptic, and very location-based. You will see them hop from spot to spot, then lock down and watch the world. They can be surprisingly bold once they learn you are the food person, but they are not built to compete with fast feeders.

• Good tankmates: small, peaceful fish that do not harass perching fish (think tiny gobies that mind their own business).
• Risky tankmates: wrasses, dottybacks, hawkfish, bigger gobies, and anything that picks at rock faces or investigates every crevice.
• Inverts: most reef-safe inverts are fine, but watch crabs and large shrimp. If it can pin a small fish, it might.
• Other clingfish: I would not pair them unless you have a plan and space. They can get territorial about a favorite perch.

Breeding tips

Breeding clingfish in home tanks is possible in the broader group, but for Tomicodon lavettsmithi it is not something you see documented often. The big hurdle is usually not getting eggs, it is raising tiny larvae that need the right live foods at the right size and density.

• If you want to try: run a dedicated small system with mature rock and calm zones.
• Conditioning: heavy feeding with varied meaty foods and lots of pods tends to bring out courtship behavior in many small cryptic fish.
• Spawning site: offer tight caves and undersides of rocks. Some clingfish lay in protected spots.
• Larval plan: be ready with rotifers, copepod nauplii, and greenwater technique. If you do not already culture live foods, start there first.

Common problems to watch for

Most losses I have seen with clingfish come down to feeding and mechanical hazards, not mysterious disease. They are tough in some ways, but they do not tolerate being outcompeted or sucked into equipment.

• Starvation: the fish hides, gets a pinched belly, and stops responding to food. Fix by target feeding, reducing competition, and increasing small live foods.
• Pump/overflow accidents: missing fish that "vanished" is often this. Guard everything.
• Stress from aggressive tankmates: torn fins, constant hiding, or being pushed off perches.
• Shipping damage and dehydration: tiny fish can arrive rough. Dim lights, offer live foods, and do not chase them around the tank.
• Medication sensitivity: in a reef tank you are limited anyway, but be cautious with harsh treatments. Use a separate hospital tank if you need to treat.

If you build the tank with their lifestyle in mind and you are willing to target feed, they are incredibly rewarding. You end up watching a whole different layer of reef behavior that most fishkeepers never notice.