Otocinclus Tank Mates: 22 Species Rated ○△× with Reasons, Why They Get Bullied, Medaka, Goldfish, Shrimp, Algae and Food

In short: which fish are safe tank mates for otocinclus?

Otocinclus are safe with peaceful small fish, bottom dwellers and adult shrimp. The three to avoid are the betta (male), the angelfish and the goldfish.

Otocinclus are small catfish that live by grazing algae on glass and plants. Shop guides also introduce them as fish that are easy to keep with others.

The trouble is that because they attack no one, they easily end up bullied or losing their food. This site works out compatibility with 22 species and shows it with reasons.

What this article covers:

• Compatibility with 22 species, and why some pairs are × or △
• Why they tend to be the ones that get bullied
• How to handle them with medaka, goldfish and shrimp
• What you can expect from them as algae eaters
• Why algae alone is not enough food, and how many to keep

Source: Judged by this site's rules from the care data of each species (see the sources of the care data table)

The list above, grouped by result:

The key point: otocinclus tank mates come down to two things: "does the partner attack?" and "does food reach the otos?"

In what order should you check otocinclus tank mates?

Check otocinclus tank mates in this order: temperature, mouth size, temperament, then shrimp. The three × species fail at the second or third step.

Applied to otocinclus, the four steps look like this.

The order matters. A partner whose temperature does not match cannot live long with otos, even if everything else matches.

Otocinclus do not attack others, so what you check is the partner's side: what will the partner do?

Why do otocinclus get bullied?

Otocinclus get bullied easily because they are small, timid and peaceful. Paired with aggressive fish or big-mouthed fish, they end up chased or eaten.

Tokyo Aqua Garden describes the otocinclus as gentle and somewhat timid. It also writes that otos never chase other fish.

Here are fish that often bully otos, with their size and temperament.

Source (5)

• Seriously Fish (Betta splendens)
• Seriously Fish (Pterophyllum scalare)
• Seriously Fish (Otocinclus macrospilus)
• Seriously Fish (Puntigrus tetrazona)
• RSPCA Australia: How should I care for my goldfish?

As the table shows, the × and △ partners are all bigger than otocinclus and differ in temperament. The gap shows up in four ways.

Seriously Fish describes otocinclus as very timid. It also writes that they lose out to active fish when competing for food.

Search suggestions show "dying" and "cause of death" next to "bullied." The same source says most deaths of newly imported otos come from lack of food.

Even without obvious chasing, assume there may be bullying in the form of food being taken again and again, and keep watching.

Which fish are × as otocinclus tank mates?

The × species are the betta (male), the angelfish and the goldfish. Bettas chase them, and the other two have a size gap big enough to swallow them.

Angelfish are often still small when sold in shops. While small they can swim together, but their mouths change as they grow.

Search suggestions also show "betta otocinclus tank mates." Compatibility from the betta's side is in Betta Tank Mates.

For the three × species, more hiding places do not remove the reason, so the shortcut is never to put them in the same tank.

Can otocinclus live with medaka?

Otocinclus with medaka are △ (with conditions). The temperature overlap is narrow, and it pairs a fish that needs a heater with one that does not.

Search suggestions also show "otocinclus medaka tank mates." Both are peaceful fish, and they swim at different levels.

Source: Seriously Fish (Otocinclus macrospilus) / Seriously Fish (Oryzias latipes)

As the table shows, the temperatures overlap only in a narrow band at the edge of each range. Seriously Fish describes medaka as a temperate to subtropical fish.

The same source says always-warm water can shorten medaka's lives. Heating the water for otocinclus keeps it warm for the medaka.

If you keep them together, follow these points.

• Check the thermometer every day and keep the water inside the overlap in the table
• Watch out for both high temperatures in summer and cold in winter
• Do not rely on the medaka's food. Give the otocinclus their own share

The two species share a narrow temperature band, so separate tanks are easier to manage. Compatibility from the medaka's side is in Medaka Tank Mates.

Can otocinclus live with goldfish?

Otocinclus with goldfish are ×. Otocinclus are small enough to fit in a goldfish's mouth, and their heater needs differ.

Search suggestions also show "goldfish algae eater otocinclus." The oto's name often comes up as an algae eater for goldfish tanks.

RSPCA Australia says goldfish partners should be limited to fish larger than the goldfish's mouth. Goldfish need no heater, while otocinclus do.

For algae in a goldfish tank, looking for a different animal is the shortcut. Check goldfish and snail compatibility in Goldfish Tank Mates.

Rather than adding otocinclus to a goldfish tank, first think about tank care that keeps algae from growing.

Can otocinclus live with shrimp?

Otocinclus with Amano shrimp are ○, and with Neocaridina shrimp and red cherry shrimp they are △. The △ is because otos sometimes pick at baby shrimp.

○ Generally compatible　△ With care　× Not recommended

Source: Judged by this site's rules from the care data of each species (see the sources of the care data table)

Aquarium Co-Op writes that otocinclus sometimes pick at baby shrimp. On the other hand, it says adult shrimp usually survive.

The same shop also writes that keeping them with fry or baby shrimp caused little harm. △ means "the adults survive, but breeding may slow down."

Amano shrimp larvae grow up in the sea. No baby shrimp are born in a freshwater tank, so there is no worry about otos eating them in the first place.

Shrimp and otocinclus both eat algae and food on the bottom, so watch the amount of food for both. Compatibility from the shrimp's side is in Shrimp Tank Mates.

How much can you expect from otocinclus as algae eaters?

Otocinclus are good at soft algae such as brown algae. They do not eat hard algae such as black beard algae, so set your expectations by the type of algae.

Many people add them as algae eaters. Here are the algae the sources say they eat and do not eat.

Seriously Fish recommends a tank with plenty of broad-leaved plants and driftwood. More surfaces for algae to grow on means more places to graze.

But each oto's algae-eating power is not that great. Some shop guides suggest pairing them with shrimp or snails.

Otocinclus help keep soft algae from spreading. Do not think of them as fish that wipe out all the algae, and you will not be let down.

Is algae enough food for otocinclus?

Algae alone is often not enough food for otocinclus. Seriously Fish describes them as fish that need to eat almost constantly.

The same source says food in the aquarium should be mainly plant-based. They also eat live and frozen foods such as bloodworms, but it advises not to overfeed these.

Tokyo Aqua Garden describes a way to get them used to food: put boiled spinach in together with prepared food. It says it takes time for them to learn it is food.

In a community tank, do not leave otocinclus with what the other fish leave behind. Prepare their food separately and get it to them. Check how round their bellies are every day to see if they are eating enough.

How many otocinclus should you keep?

Base the number on the group size (see the table), then adjust for the amount of algae. Seriously Fish says they like their own kind, so it recommends keeping a group.

Search suggestions show "how many," "how many in a 60 cm tank" and "how many in a 30 cm cube." The sources take two approaches.

Aquarium Co-Op says a few plump fish are better than a thin group. Before numbers, check that every fish gets to eat.

The more you add, the less algae each one gets, so the limit is whether you can add enough food. Think about group size and floor space together with the other bottom dwellers.

Can otocinclus live with corydoras, plecos and other bottom dwellers?

Yes. Otocinclus are ○ with corydoras, kuhli loaches and bristlenose plecos.

○ Generally compatible　△ With care　× Not recommended

Source: Judged by this site's rules from the care data of each species (see the sources of the care data table)

In this site's table, otocinclus are bottom-level fish. But Seriously Fish says they spend a lot of time off the bottom.

That suggests they rarely compete for space with corydoras, which search the bottom. Seriously Fish also names smaller corydoras as partners.

The quick chart above has a × and a △ involving shrimp.

• Kuhli loach × Neocaridina shrimp: often eats baby shrimp
• Otocinclus × Neocaridina shrimp: sometimes picks at baby shrimp

When you add bottom dwellers, check not only their compatibility with otocinclus but also with shrimp. The corydoras's side is in Corydoras Tank Mates.

What middle and top level fish should you choose with otocinclus?

For the middle and top levels, choose peaceful small fish such as neon tetras, rasboras, guppies and platies. All are ○ with otocinclus.

Seriously Fish names small, peaceful characins as partners. Characins are the group that includes tetras. Its dwarf gourami entry also calls otocinclus a particularly good partner.

But even among ○ partners, some move fast at feeding time. Aquarium Co-Op recommends partners that will not outcompete otos for food: peaceful fish of about the same size.

When choosing from ○ partners, pick ones that let food reach the otocinclus at feeding time, and you will have fewer failures. The neon tetra's side is in Neon Tetra Tank Mates.

What should you do before adding otocinclus to a community tank?

Before adding otocinclus, prepare a settled tank with algae and plants. Watch new fish in a separate tank before adding them.

Seriously Fish says otos have few problems when added to a settled planted tank. Newly imported fish are often weak.

Steps before adding, in order:

1. Let the main tank run until algae and biofilm grow
2. Watch new fish in a separate tank for at least 30 days (University of Florida)
3. Provide algae or extra food in the quarantine tank too
4. Get them used to the main tank's water little by little, then release them
5. For a few days after release, check that they are eating

Aquarium Co-Op leaves the light on in the quarantine tank for about a week. The idea is to grow algae first.

For otocinclus, "last, into a settled tank" is the way to make tank mates last.

What are common mistakes with otocinclus tank mates?

The three most common mistakes are: adding them to a newly set up tank, relying on algae for food, and pairing them with big fish.

If you see it is not working, separate the chaser or the weakened fish with another tank or a divider. The basic fix for a bad match is to separate them, not to make them put up with it.

What terms come up with otocinclus tank mates?

What else goes with otocinclus tank mates?

Otocinclus tank mates connect to bottom dwellers, shrimp and middle level fish. Go on to the article for the partner you are curious about.

• Partners that share the bottom: Corydoras Tank Mates
• Shrimp and snails: Shrimp Tank Mates
• Partners in the middle level: Neon Tetra Tank Mates
• All 22 species at once: Tropical Fish Tank Mates Chart

Frequently asked questions about otocinclus tank mates

Which fish can live with otocinclus?

Peaceful small fish, bottom dwellers, and adult shrimp and snails suit them. Of this site's 22 species, 15 are ○.

The ones to avoid are the betta (male), the angelfish and the goldfish. Pick two species to see the result and the reason.

Why do otocinclus get bullied?

Because they are small, timid and peaceful. Aggressive fish chase them, and active fish take their food.

Choose partners from peaceful fish of about the same size.

Can otocinclus live with medaka?

With conditions. They are △: the temperature overlap is narrow, and their heater needs differ.

If you cannot keep the water inside the overlap, separate tanks suit them.

Can otocinclus live with Neocaridina shrimp?

Yes, but they are △. Otos sometimes pick at baby shrimp, while adult shrimp survive.

If you want the shrimp to breed, grow thick clumps of plants.

Can otocinclus live on algae alone?

Algae alone is often not enough. They eat almost constantly, and a lot of them will eat all the algae.

Give blanched vegetables or sinking plant-based food separately.

How many otocinclus should you add?

Base it on the group size (see the table), then decide by the amount of algae and whether you can add food. Keep fewer in a small tank.

If every fish has a nicely rounded belly, the number is right.

Sources

• Seriously Fish: Otocinclus macrospilus (very timid and loses food to active fish, keep a group, spends a lot of time off the bottom, floor space, broad-leaved plants and driftwood, mainly plant-based food, do not overfeed live food, newly imported fish often die from lack of food, few problems in a settled planted tank, small characins and smaller corydoras as partners, mislabeling in shops)
• Seriously Fish: Betta splendens (bettas are best kept alone)
• Seriously Fish: Pterophyllum scalare (angelfish may eat small fish once grown)
• Seriously Fish: Oryzias latipes (medaka are temperate to subtropical fish, warm water and lifespan)
• Seriously Fish: Trichogaster lalius (otocinclus are a particularly good partner for dwarf gouramis)
• RSPCA Australia: How should I care for my goldfish? (goldfish partners must be larger than the goldfish's mouth)
• UF/IFAS EDIS FA006: Ichthyophthirius multifiliis (White Spot) Infections in Fish (watch new fish for at least 30 days)
• UF/IFAS EDIS FA124: The Ornamental Fish Trade (watching before adding, acclimating to the water)
• Aquarium Co-Op: Otocinclus Catfish (choose peaceful partners, eats soft algae and diatoms but avoids hard algae, lack of food is the weak point, blanched vegetables and tablets, too many eat all the algae, grow algae in the quarantine tank, little harm with baby shrimp)
• Aquarium Co-Op: Cherry Shrimp Tank Mates (otocinclus sometimes pick at baby shrimp but leave adult shrimp)
• Tokyo Aqua Garden: How to keep otocinclus (オトシンクルスの飼育方法, in Japanese. Gentle and somewhat timid, eats brown algae but not black beard or blue-green algae, 1 to 2 in a small tank, getting them used to food with spinach and prepared food)