Otocinclus with shrimp

By the Shrimp Tank Hub editorsUpdated Oct 25, 2026Research-based

Otocinclus ("otos") are small South American suckermouth catfish, a genus of about 20 species; the ones usually sold include O. vittatus, O. macrospilus and the zebra oto, O. cocama (Aquarium Co-Op). They graze algae and biofilm instead of hunting, which is why shrimp keepers like them so much. With otos the shrimp are rarely the ones at risk. The usual problem is keeping the otos alive.

Otocinclus at a glance

Will otocinclus eat shrimp?

This is the one fish where the sources agree almost completely:

• The Shrimp Farm (tankmates guide): ranks otos its number one shrimp tankmate, rated "top-tier", because they are too small and their mouths the wrong shape to eat even baby shrimp.
• The Shrimp Farm (care guide): says otos are one of the few species in the trade, maybe the only one, unlikely to eat even newly hatched shrimp.
• Practical Fishkeeping: says algae-eaters aren't interested in shrimp and often can't eat them, and names Otocinclus and their relatives Parotocinclus and Hypoptopoma as the main shrimp-safe candidates.
• Aquarium Co-Op: lists dwarf shrimp among good oto tank mates, and says it has housed otos with baby fish and shrimp with minimal casualties.

"Minimal" is the honest word: Aquarium Co-Op notes that all fish will opportunistically eat whatever fits in their mouths. But for a breeding colony, otos are the fish least likely to slow it down. Compare pygmy corydoras and kuhli loaches, other bottom fish that do take some shrimplets, and see cherry shrimp tank mates.

The real risk: starving otos

Both sources say the same thing: otos rarely die of disease; they usually die because they don't get enough to eat. Aquarium Co-Op explains why. Most otos are wild-caught, fasted at the exporter so they make less waste in shipping, then kept by the hundreds in bare wholesaler tanks. By the time they reach a store they may not have eaten well for 3 to 6 weeks.

The Shrimp Farm adds that otos, like Sulawesi shrimp, don't seem able to live on prepared food alone. They need a steady supply of algae and biofilm, which a newly cycled tank doesn't have. Its test: if uncleaned glass doesn't feel thin, slippery and slimy, the tank is too clean for otos.

This matters for shrimp keepers in particular, because shrimp graze the same biofilm. A small tank with a dense colony may already be grazed bare, so otos need a bigger, older tank than their size suggests. More on biofilm in what shrimp eat and driftwood and botanicals.

Matching the water

Otos are flexible on pH, hardness and temperature, but very sensitive to poor water quality: The Shrimp Farm says they can't tolerate any ammonia or nitrite, or nitrate above 20 ppm. The overlap with cherry shrimp is easy:

The shared zone is our comparison of the published ranges, not a tested target. Soft-water Caridina such as crystal red shrimp kept below pH 7 also fall inside the oto's range. See ammonia and nitrite, nitrate in a shrimp tank and shrimp tank pH.

Tank size and setup

• Size: The Shrimp Farm says otos can technically live in 10 gallons but prefers 20 or more, because they are sensitive to water quality and need room to graze. Its tankmates guide lists 15 gallons or more. See how many shrimp per gallon.
• Age: wait. The Shrimp Farm says not to buy otos for a brand-new tank, and to have the nitrogen cycle rock solid first. See how to cycle a shrimp tank.
• Algae surfaces: Aquarium Co-Op suggests slow-growing, flat-leaved plants such as Anubias that collect algae, and cleaning only the front glass so algae keeps growing on the other three sides. See best plants for a shrimp tank and algae in a shrimp tank.
• Wood and leaves: both sources like driftwood, and The Shrimp Farm keeps plenty of Indian almond leaves and other leaf litter, which become biofilm factories as they decay. Shrimp graze the same film.
• Calm tankmates: The Shrimp Farm warns that large or greedy fish, including plecos, outcompete timid otos for food. Shrimp, snails and small peaceful fish are a good fit.

Feeding two grazers

In a very large, long-established tank otos may never need extra food, but The Shrimp Farm says most tanks need supplements. Foods both sources mention:

• Gel food such as Repashy Soilent Green, which The Shrimp Farm suggests painting on rocks or wood so it sets like biofilm.
• Blanched vegetables: zucchini (both sources), spinach (The Shrimp Farm) and green beans (Aquarium Co-Op).
• Algae wafers and tablets and nori sheets.
• Protein sparingly: The Shrimp Farm warns too much protein can cause bloat.

Shrimp will swarm the same foods, which is fine, but watch that the otos get some. Remove leftovers so they don't foul the water; see best shrimp food.

Buying and adding otos

• Grow algae first. Both sources suggest a quarantine tank set up in advance with the light left on (Aquarium Co-Op says a week or so; The Shrimp Farm says 2 to 4 weeks, seeded with bacteria from the display tank) so it's covered in algae when the otos arrive. See how to quarantine.
• Buy early, buy plump. Aquarium Co-Op suggests buying the day after a shipment arrives, before the store tank is grazed bare, and choosing otos with round, pearly bellies that are actively feeding. Once a starved oto stops eating it is hard to get it feeding again.
• Keep the group small. About 4 (The Shrimp Farm) is plenty for most shrimp tanks.
• The first two months are the test. Aquarium Co-Op says otos that have lived in your tank for more than a month or two are getting enough food.
• No medications in the shrimp tank. Practical Fishkeeping notes many fish medications are not safe for invertebrates. If an oto looks sick, ask a fish veterinarian or an experienced store about shrimp-safe options. See is copper toxic to shrimp.

Common mistakes

• Adding otos to a newly cycled, spotless tank.
• Buying a big school "because they're schooling fish".
• Buying the skinniest, hollow-bellied otos from a grazed-bare store tank.
• Scraping every pane of glass clean.
• Expecting otos to fix black beard or green spot algae; they eat soft algae (Aquarium Co-Op).

Track it

Log temperature, pH, GH and TDS on the free Water Parameter Log printable so you can keep the tank in the range both species share.

Frequently asked questions

Can otocinclus live with cherry shrimp?

Yes. The Shrimp Farm rates otos the best tankmate for shrimp and Practical Fishkeeping calls them 100% safe. The harder part is keeping the otos well fed.

Will otocinclus eat baby shrimp?

Very unlikely. The Shrimp Farm says their small, grazing mouths can't eat even newborn shrimp, and Aquarium Co-Op reports minimal casualties with baby shrimp.

Why do my otocinclus keep dying?

Usually starvation. Many otos arrive underfed after weeks in export and wholesale tanks, and a new or spotless tank has too little algae and biofilm for them (Aquarium Co-Op, The Shrimp Farm).

How many otocinclus should I keep with shrimp?

A small group, about 4 (The Shrimp Farm). Too many will graze the tank bare; Aquarium Co-Op says a couple of plump otos beats six starving ones.

What size tank do otocinclus and shrimp need?

15 gallons or more is easier; The Shrimp Farm says 10 gallons is the bare minimum and prefers 20 or more.

Do otocinclus compete with shrimp for food?

Yes, both graze biofilm and soft algae. Give the tank time to mature, add leaf litter and wood, and supplement with gel food and blanched vegetables.

Will otocinclus clean up all the algae?

Only soft algae such as green film and brown diatoms. Aquarium Co-Op says they avoid black beard and green spot algae.

Sources: Aquarium Co-Op, Otocinclus catfish care guide (about 20 species, common O. vittatus, O. macrospilus, O. cocama; 1.5–2 in; eat soft green algae, diatoms and biofilm, avoid black beard and green spot; most wild-caught, fasted and underfed for 3–6 weeks before stores; greatest weakness is not enough food; algae-filled quarantine tank, buy the day after arrival, pick round pearly bellies; success if alive after a month or two; 70–79 °F, pH 6.0–7.5, soft to hard; mature, planted tank with algae, biofilm and wood; Anubias, clean only the front glass; don't overstock; tank mates include dwarf shrimp, housed with baby fish and shrimp with minimal casualties; zucchini, green beans, wafers, Repashy); The Shrimp Farm, Otocinclus care (10 gallons technically, 20+ preferred; sensitive to water quality; most die from starvation, not disease; need constant biofilm and algae like Sulawesi shrimp; slimy-glass test; leaf litter and long light periods to grow biofilm; no ammonia or nitrite, nitrate under 20; pH 5.5–7.5, 70–79 °F, TDS 50–250; group of at least 4, not an army; no large or voracious fish including plecos; unlikely to eat even newly hatched shrimp; gel food painted on decor, algae tablets, blanched zucchini and spinach, nori, protein sparingly; quarantine tub with lights on for 2–4 weeks); The Shrimp Farm, Shrimp tankmates and compatibility (Otocinclus up to 1.4 in, 15+ gallons, moderate–hard, top-tier shrimp safety, mouths can't eat baby shrimp); Practical Fishkeeping, What can I keep with shrimp? (algivores won't eat shrimp; Otocinclus, Parotocinclus and Hypoptopoma 100% safe; many medications not invertebrate-safe). Cherry shrimp ranges from our cherry shrimp care guide (The Shrimp Farm). Checked October 25, 2026.