Striped blenny

Where they come from

Striped blennies (Chasmodes bosquianus) are little coastal fish from the western Atlantic - think salt marshes, tidal creeks, oyster beds, and weedy shoreline zones. They live where the water changes all the time: tides rolling in and out, rain dumping fresh water, summer heat, winter chill. That background tells you a lot about why they are tough in some ways, but weirdly picky in others.

Setting up their tank

If you want these guys to settle in, build the tank like a shallow shoreline with lots of cover, not an open glass box. They are perchers and hiders. Give them places to wedge into, and they will actually come out and show personality.

• Tank size: 20 long is a nice starting point for one. Bigger is better if you are trying pairs or tankmates.
• Salinity: aim for stable brackish, not swinging all over the place. I have had the best results around SG 1.005-1.010 (measure with a refractometer if you can).
• Temp: mid 70s F works well for most people (around 72-78F). They can handle cooler seasons, but stability helps in aquariums.
• Hardscape: piles of small rock, oyster shell, barnacle clusters, PVC elbows hidden under rock, and snug caves. Tight openings matter.
• Substrate: sand is easy. A little shell grit mixed in feels natural and buffers a bit.
• Flow and filtration: moderate flow, not a blast zone. Use good mechanical filtration because they are messy eaters.

Lighting does not need to be intense. I actually prefer a slightly dimmer tank with some macroalgae or tough brackish plants if you can manage them. Even just letting some green film algae grow on rocks helps, because it makes the tank feel more like their home turf.

What to feed them

They are enthusiastic little predators. Mine ignored flakes and most pellets at first, then slowly learned. Live and frozen foods are your best tools for getting a new striped blenny eating with confidence.

• Best starters: live blackworms (if you can get them), live or frozen brine shrimp, frozen mysis, chopped krill, and small pieces of raw shrimp or clam.
• Once settled: good frozen mixes, finely chopped seafood, and small sinking pellets (train them by mixing pellets into mysis).
• Feeding style: small meals 1-2 times a day beats one huge dump. They pick and stalk, and big feedings foul water fast.

You will also notice them pecking at rock and glass. That is normal grazing behavior, but do not count on it as their main diet. They still need meaty food to keep weight on.

How they behave and who they get along with

Striped blennies have that classic blenny attitude: curious, bold on their terms, and very attached to a favorite hole. They are not open-water swimmers. Most of the time you will see them perched on rock, poking their head out, then darting back in.

• Territory: they will claim a cave and defend it, especially males.
• Tankmates: choose calm brackish fish that will not outcompete them at feeding time or constantly invade their hideouts.
• Avoid: fin nippers, fast aggressive feeders, and anything that will treat them like a snack.

I have had the least drama keeping one striped blenny as a feature fish in a brackish setup. Groups can work, but you need space, line-of-sight breaks, and multiple caves. Two fish in a small tank is where people get stuck with nonstop squabbling.

Breeding tips

Breeding is doable, but it is not a casual weekend project. They are cave spawners. The male usually guards eggs in a tight shelter and fans them. Getting a compatible pair is the hard part, and raising larvae is the real challenge.

• Give options: several narrow caves (small PVC, barnacle clusters, rock crevices) so a male can pick a nest site.
• Conditioning: feed heavy on meaty frozen/live foods for a few weeks.
• Behavior clue: a male that stays near one cave and chases others away is often setting up shop.

Common problems to watch for

• Not eating after purchase: usually stress plus too much light/too little cover. Add hides, dim the tank, and offer live/frozen foods at the cave.
• Getting bullied or outcompeted: they are slow, deliberate feeders. In a busy tank they can starve while looking "fine" for weeks.
• Salinity swings: topping off with saltwater instead of fresh (or the opposite) can push SG around and stress them hard.
• Skin and fin infections: often follow abrasions from squeezing into sharp rock or oyster shell. Keep water clean and watch for ragged fins.
• Ich/parasites: brackish fish can still get parasites. Quarantine helps a lot, but match salinity during transfers so you are not piling stress on stress.
• Nitrate creep: heavy feeding plus a small brackish tank equals slow water-quality decline. Regular water changes beat chasing problems with additives.

If you keep the salinity steady, give them real shelter, and feed like you mean it, they are genuinely fun fish. Mine would watch me from its cave like a grumpy neighbor, then rocket out for mysis the second the baster hit the water.