Kelp gunnel
Ulvicola sanctaerosae
The Kelp gunnel features a slender, elongated body with a mottled brown-green coloration and a distinctive, continuous dorsal fin.
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About the Kelp gunnel
This is a skinny little kelp-forest perch that literally hangs out up in the kelp canopy and chills on the fronds. One of the coolest bits is how it uses its tail to wrap onto kelp like a grip, then picks off tiny crustaceans drifting by. Not really an aquarium trade fish, but its a super neat West Coast oddball if you ever see one while diving.
Quick Facts
Size
29 cm
Temperament
Peaceful
Difficulty
Expert
Min Tank Size
55 gallons
Lifespan
3-6 years
Origin
Eastern Pacific (West Coast North America)
Diet
Carnivore - small crustaceans; in captivity would be meaty frozen foods like mysis/amphipods
Water Parameters
10-18°C
8-8.4
8-12 dGH
Need a heater for this species?
This species needs 10-18°C in a 55 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a coldwater marine tank with legit kelp or macroalgae and lots of rock cracks - they want to snake through tight spots and will stress out in open, bright reef-style layouts.
- Keep temps on the chilly side (roughly 50-60F / 10-16C) with a chiller and steady salinity around 1.023-1.026; warm water is the fastest way to end up with a not-eating gunnel.
- They are jump-and-squeeze artists, so seal the lid, block tiny gaps around plumbing, and cover overflows - if there is a hole the width of a pencil, they will test it.
- Feed meaty, marine foods: chopped shrimp, mysis, clam, krill, and small silversides; target feed with tongs so the food hits the bottom near their hideouts.
- Plan on 3-5 small meals per week (or small daily feeds if your filtration can take it) and remove leftovers fast - they foul water easily when overfed.
- Tankmates: think other coldwater, non-bully fish that will not outcompete them at feeding time; avoid aggressive wrasses, trigger-type personalities, and anything that can fit them in its mouth.
- Watch for skin scrapes and fin damage from rough rock and frantic bolting, plus parasites that show up after wild collection; a quiet quarantine and keeping the water cold goes a long way.
- Breeding is rare in home tanks, but if you try, mimic seasonal cooling/warming and offer dense algae for egg laying; adults may snack on eggs, so pull the clutch or separate the pair.
Compatibility
Good Tankmates
- Other small, peaceful coldwater fish that mind their own business - think cleaner shrimp-safe, non-territorial types that cruise and dont pick fights (small sculpins and similar mellow locals can work if they are not the gulp-everything kind).
- Peaceful gobies and blennies that stick to their own patch and arent super pushy at feeding time. The kelp gunnel is more of a sneaky rock-and-kelp hanger, so calm neighbors are best.
- Small, non-aggressive wrasses (the chill, coldwater-appropriate ones) that dont constantly harass rockwork. As long as theres lots of cover, they mostly ignore each other.
- Pipefish or seahorse-style slowpokes - only if you are set up for them and the gunnel is well-fed. In my experience the gunnel is usually peaceful, but its still a little predator and can get curious around tiny tankmates.
- Non-fishy tankmates like snails, urchins, and tougher stars - the gunnel is usually fine with them and mostly just uses the rockwork and algae as a jungle gym.
- Other kelp gunnels in a roomy, kelp/rock-heavy tank with lots of hidey-holes. They are generally peaceful, but crowd them and you can get bickering over favorite caves.
Avoid
- Big, mouthy predators like larger sculpins, lingcod-style fish, or any 'if it fits it ships' hunter. They will treat a gunnel like a snack sooner or later.
- Aggressive, territorial rock bullies that claim the whole reef and chase nonstop (think mean damsel-type behavior). The gunnel will stay hidden, get stressed, and stop eating well.
- Fast, nippy fish that constantly peck fins and faces, especially ones that harass anything that perches in the rocks. The gunnel is peaceful and loses that battle every time.
- Tiny bite-sized fish or shrimp you actually want to keep long term. Even a peaceful gunnel will opportunistically slurp very small tankmates if the chance is there, especially at night.
Where they come from
Kelp gunnels are cold-water, kelp-bed fish from the northeastern Pacific. Picture a fish that lives its whole life weaving through kelp fronds and rocky cracks, hunting tiny critters and vanishing the second you look away. That whole "hide first, ask questions later" vibe is basically their personality.
If your system is more "tropical reef" than "cold kelp forest," this is the part where most attempts go sideways. They are a cold-water animal.
Setting up their tank
Think less open swimming space, more structure. Mine spent most of the day tucked into rockwork or laid along algae like a little ribbon. If the tank is sparse, they stay stressed, stop eating, and you will only see them at 2 a.m.
- Temperature: cold. Aim for roughly 48-58 F (9-14 C). Stability matters more than chasing a single number.
- Salinity: normal marine range (around 1.024-1.026). Keep it steady.
- Filtration: heavy on oxygenation and flow, but not blasting their favorite caves. They come from surge-y, oxygen-rich water.
- Aquascape: piles of rock with tight crevices, plus macroalgae (kelp/rockweed style if you can) or at least tough macros they can wind through.
- Substrate: sand or fine gravel is fine, but the rockwork is what they care about.
- Lighting: moderate is plenty. If you run strong lights, give them shaded zones so they can get out of it.
A chiller is basically non-negotiable for most homes. Room-temp water for long stretches is a slow loss with this species.
Lids matter. They are not famous jumpers like some wrasses, but gunnels will slither and launch if spooked, especially during netting or sudden light changes. Cover gaps around plumbing too.
What to feed them
They are little predators. Mine did best on meaty, bite-sized foods offered regularly. Once they recognize you as the food source, they get bold fast, but the first couple weeks can be a bit of a hunger strike if they do not feel secure.
- Staples: chopped shrimp, mysis (bigger frozen mysis is great), finely chopped clam, krill pieces (not as the only food), squid bits
- Live/fresh to kickstart feeding: live amphipods, small live shrimp, live blackworms (rinse well, use sparingly), freshly cracked mussel
- Feeding rhythm: small meals 4-6x/week beats one huge feeding. They are built to pick at prey in the weeds.
- Target feeding: use tongs or a turkey baster to place food near their hide. They learn this routine quickly.
If it ignores food in the open water, feed the tank, wait a minute, then gently squirt a couple pieces right to its crack in the rocks. That was the switch that got mine going.
Avoid feeder fish. Besides the disease risk, they get fat in a weird way and you miss out on the chance to keep nutrition varied.
How they behave and who they get along with
Kelp gunnels are sneaky, perchy, and surprisingly opinionated about their personal space. They are not "community fish" in the tropical sense. They will ignore big tankmates, but anything small enough to fit in their mouth eventually looks like food.
- Good tankmates: other cold-water fish that are not aggressive and not bitey (think mellow rockfish species, sculpin-type fish with compatible temps, depending on local legality and collection rules)
- Avoid: nippy fish, fast bullies, anything tiny (shrimp, small crabs, tiny gobies/blennies), and anything that insists on the same exact cave
- Inverts: expect predation on small crustaceans. Larger, well-armored inverts sometimes last, but I would not count on it.
- Territory: give multiple caves and "lanes" through the rock so they do not have to share a single hide.
They can look peaceful for weeks, then one day a small tankmate vanishes. If it fits, it is on the menu.
They spook easily at sudden changes. I had better behavior once I stopped doing abrupt light flips and started ramping the room lights first, then the tank lights.
Breeding tips
Breeding in home aquariums is uncommon, mostly because you need true seasonal cues and a stable pair that actually likes each other. In the wild, they tie spawning to seasons, day length, and cool water. If you are serious, you are basically running a mini cold-water biotope with a calendar.
- Start with a well-fed, well-established pair or small group and let them sort it out over months
- Provide dense macroalgae and rubble zones where eggs could be placed and guarded
- Mimic seasons: gradually shift photoperiod and keep temps on the cooler end for extended periods
- Have a plan for larvae: if they go pelagic, you are in rotifer/phytoplankton territory fast
If your goal is just to keep one healthy long-term, skip the breeding rabbit hole. Focus on cold, clean, oxygen-rich water and steady feeding.
Common problems to watch for
Most problems I have seen with gunnels are not mysterious diseases. It is usually the environment: too warm, not enough oxygen, or not enough cover. Fix those and a lot of "mystery" issues disappear.
- Heat stress: rapid breathing, hiding constantly, refusing food. This is the big one.
- Low oxygen: hanging in high-flow areas, gulping, acting "off" at night. Add surface agitation and flow, clean pumps, watch clogged intakes.
- Refusing food after arrival: usually stress + no secure hide. Darken the tank, add cover, and target feed near the den.
- Skin damage from nets/rough rock: they wedge into tight spots and can scrape. Use soft nets or better, a container to move them.
- Parasites from wild collection: observe in quarantine if you can, and do not mix with delicate species right away.
- Copper and meds: be cautious. Cold-water fish can react differently, and sudden parameter swings hit them hard.
Do not try to "make it work" at tropical temps. It might eat for a while and look fine, then crash months later. Keep it cold from day one.
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