If you’re looking for a cute, friendly fish to add to your tank, the Oto catfish is an excellent choice.
These small algae eaters are loved by fishkeepers for their appearance, good personality, and algae cleaning skills. Otocinclus catfish are peaceful fish that will get along with other species of similar size and temperament. They won’t bother your plants or decorations either! This makes them very popular fish for community tanks.
Even though they’re an easy-going fish species, you will still want to learn what they need in order to keep them happy and healthy. Our Oto Catfish care guide covers their appearance, ideal habitat, feeding, breeding, and more. Let’s dive in!
Table of Contents
Recommended Oto Catfish Care Items:
Oto Catfish Overview
Otocinclus is a genus of freshwater catfish from the family Loricariidae which belongs to the order Siluriformes. They are native to the lakes, rivers, and estuaries of South America, primarily in Argentina and Venezuela.
There are around 19 species of Otocinclus and they come in different colors, sizes, and patterns. They’re also commonly called otos, ottos, dwarf suckers, dwarf suckermouths, dwarf oto, dwarf ottos, dwarf suckers, and algae scrapers.
They’re most active during the day which means you’ll get to see them in their daily jobs of cleaning up algae in your tank. They are also shoaling fish so you will want to keep more than one oto around to keep them happy.
Oto Catfish Appearance
Size-wise, Oto catfish are small. Adults rarely exceed 2 inches. This means they’re great options for small tank algae eaters.
Their body is a short cylinder that tapers towards the head and tail fin. They have a strong sucker mouth which is their pride and joy of algae eating.
They differ from other catfish species because they have rows of armor plating their body (somewhat similar to a twig catfish). They don’t have any scales, as they’re covered in tiny plates instead. These plates help protect these little guys from larger fish and rough substrates.
Interestingly, Oto catfish have an air-filled sac near their esophagus that provides additional buoyancy and helps them swim at higher levels in the tank. Most armored catfish are heavy and will sink because of their plate weight.
There are many different species of Oto catfish and they can look quite different from another. Below is an overview of popular species:
Common Otocinclus (Otocinclus vittatus)
As you might expect, the Common Otocinclus is the most widely available species. In the wild, it lives across South America, including the Amazon River.
It is not the flashiest species, with a speckled brown and white body. Common Otos have a brown stripe running the length of their body with transparent fins. Its coloration helps it camouflage in its natural habitat.
Golden Oto (Otocinclus affinis)
Golden Otos are similar fish to Common Otos. As you would guess with the name, the brown colors are closer to gold. However, it can be hard to identify a Golden versus a Common Oto.
Zebra Otocinclus (Otocinclus Cocama)
You’re probably beginning to notice a pattern here. Otos’ names tend to be pretty straightforward. Golden Otos are gold and so forth.
So when you hear the name Zebra Oto, you’re correct in guessing this fish will have black and white stripes like a zebra. However, the stripes aren’t perfectly straight and sometimes look more like tiger stripes so you might hear the name Tiger Oto.
Dwarf Oto (Otocinclus macrospilus)
Dwarf Otos are most similar in appearance to Common Otos. They’re mainly brown with a similar dark stripe running the length of their bodies. However, the stripe fades before the tail fin. Their fins aren’t transparent; instead, they have a blotch of dark color on them.
Silver Otos (Otocinclus vestitus)
Silver Otos are like Golden Otos. Their brown body color is more similar to silver, as you’d guess from their name.
How long do Oto Catfish live?
In captivity, with clean tank conditions, you can expect your Oto to live between three to five years. In the wild, there are reports of Oto catfish living five to seven years.
How big do Oto Catfish get?
Otos are little fish. They top out at about two inches long when they’re fully grown. This makes them a good choice for algae duty in small tanks.
Oto Catfish Temperament
Oto catfish are generally peaceful fish. They’re also primarily active during the day which means you will see lots of energetic, entertaining behavior with these little fish. They’re great options for freshwater community tanks where you need a small algae eater. However, they can try to latch on to larger, slow-moving fish to suck the slime coat, which is not a good situation for either fish.
They’ve got a great work ethic and will spend most of their time sucking on rocks, leaves, or anything with algae growing on it. They’re constantly working to help your tank stay clean.
As mentioned before, Otos are lighter than a lot of other plated catfish, so you might catch them rising to the surface for a breath of air. This could also be a sign your tank is under oxygenated so check your water parameters if you see this behavior.
Otos will shoal together and feel most relaxed in groups of at least six. If you have a small tank and can only add one Oto, consider looking into a different species as you will really stress your Oto if you make them live solo.
Oto Catfish Care
Oto catfish are relatively easy to care for aquarium fish. However, you need to know what you’re doing. Our guide covers their ideal habitat, including tank, lighting, filtration, and more.
Oto Catfish Habitat
When planning the ideal oto tank, it is recommended to try to recreate their natural environment. This principle works well when designing tanks and making sure your fish are eating correctly. Recreate their natural environment for best results.
Otos are native to South America where they live in rivers, lakes, and other bodies of water with lots of plants and roots hanging around. Because of this, your Otos will appreciate a natural set-up with lots of plants, rocks, and driftwood.
What is the best tank for an Oto Catfish?
Otocinclus are social creatures. In the wild, they live in shoals that number in the thousands. Because of this, plan to house at least 6 in your tank at the very least. If you only have 6 Otos, a 10-gallon tank will work.
However, we recommend a larger group of Otos, in the 10-15 range if you can swing it. For that size group, we recommend a 20-gallon tank.
What We Like About This Tank
- Provides ample living space
- Includes a filter and heater
- Includes decor to provide hiding places
If you’re deciding between what size tank to purchase, remember the counterintuitive rule of fish tank sizes. Bigger tanks are easier for maintaining a healthy ecosystem because they’re less susceptible to water parameter fluctuations.
Ideal Oto Catfish Water Conditions
Maintaining water conditions is important. Use an aquarium testing kit to test your water weekly and stay on top of any changes. This is especially true in smaller tanks such as 10 and 20-gallon tanks that commonly house Otos.
Otos are sensitive to nitrates so they will require regular water testing and changes to keep them under control. The ideal water conditions for Otos are:
- Water Temperature: 72-80°F
- pH: 6-7.5
- Water Hardness: 6° to 15° dH
- Nitrates: 0-20 ppm
- Nitrite: 0
- Ammonia: 0
What to put in your Oto Catfish tank
When thinking about how to decorate your oto tank, you will want to recreate their natural habitat as much as possible. Include live plants in your tank as they can help purify the water and provide hiding places. Driftwood is another great option, and it can be used to provide nooks and crannies for hiding spots.
What is the Best Type of Substrate for Oto Catfish?
Otos are bottom-dwelling fish so the lower level tank set-up decisions are important for keeping your otos happy. We recommend either a sandy substrate or very smooth river gravel; rough rocks or gravel can scratch their body and lead to health problems.
If you go with fine-grained sand, keep in mind that some Otos like to sift through the sand looking for food. Inevitably, they will ingest some sand in the process which can lead to digestive issues. For this reason, we tend to go with very smooth river stones or pebbles which have plenty of surface area for algae but are too small for your fish to swallow.
How Much and What Kind of Lighting do Oto Catfish need?
Otocinclus don’t have major lighting needs; most standard aquarium lighting will work. Make sure you try to replicate their natural habitat as much as possible which means light during the day and darkness at night to replicate a natural cycle. If you have a planted tank, plan your light requirements around your overall plant health requirements.
What Kind of Filtration do Oto Catfish Need?
For being such little fish, Otos tend to poop a lot. This means you might need a slightly heavier dutier filtration system that you might guess just based on their size. For this, we recommend you use a canister filter with a gallon per hour (GPH) rating that is 4x the volume of your aquarium. For example, if you have a 10-gallon tank, your filter should be rated at 40 GPH.
Decorations for your Oto Tank
In their natural habitat, Otos are used to lots of vegetation, twisted tree roots, branches, and rocks. They tend to enjoy areas where they can hide from view which makes them feel safe from predators.
This is why it’s important to have lots of rocks and plants in your tank. The more hiding places you provide, the happier they’ll be. Rocks can be used to build caves for extra secure hiding spots. Avoid using sharp rocks as they can scratch their skin and cause irritations. Driftwood is another good option.
Plants are great for making your aquarium natural. You can add plants of different shapes, sizes, and colors. You can use the plants to help create additional hiding places for them. Plants are also excellent for Otos because they create more surface area for algae growth, which means more feeding opportunities.
Oto Catfish Potential diseases
Important notice: we are not veterinarians at Aquarium Friend so the information below should be used for general awareness only. If you are concerned about the health of your fish, consult a fish health professional immediately.
Otos are generally hardy little fish. However, if there are issues with the water parameters in your tank, particularly high ammonia levels, then you are likely to encounter stressed fish which tend to become sick fish. The best way to avoid this is to do your research and know your fish. Keep an eye on your water quality and test everything regularly so can focus on preventative care. If your Otos do get sick, here are some common diseases to watch out for:
- Ich (Ichthyophthirius multifilis)
- Cotton rot
- Tail rot
- Body fungus or slime
Keeping Otocinclus away from aggressive fish will also go a long way towards preventing injuries that infections can use to attack the fish. The best medicine is prevention with these fish.
If you end up treating your Otos with antibiotics, avoid antibiotics that are not certified safe for catfish and related species.
How to Purchase the Otocinclus Catfish
An important note for Otos. They are often shipped in pretty rough conditions which results in a small percentage of them dying when introduced to a new tank even though all water parameters are correct. This is just something to know about this fish species and an unfortunate side effect of the aquarium trade. Besides having low expectations for 100% survival rates, below are some tips on how to buy healthy otos.
Talk to Staff at the Local Pet Store or Fish Store
We recommend asking the following questions:
How long have they had their Otos in stock for?
A percentage of the Otos will likely die shortly after arriving at the pet store so if the shipment of Otos has been around for a while, you’ve likely avoided the first die-off.
What do you feed the Otos?
Flake food is the wrong answer. If they don’t know, that’s also a troubling sign.
Do the Otos Appear Healthy?
You’re looking for plump bellies, not overly skinny Otos. However, if the Otos are bloated and look like they’ve swallowed a marble, you will want to avoid them,
Look for saturated, radiant colors: olive-brown, black, and white. Avoid grey colors and avoid any fish with obvious nicks and cuts.
Their fins should have two sharp points at the edges. If they’ve been particularly stressed, they might be more rounded. Unless you see major fin damage, a little rounding is ok.
The Best Option? Buy Tank-Bred Otos
Easier said than done. Tank-bred Otos are going to be your best bet for health but don’t expect to find them too often.
Oto Catfish Feeding
In nature, Otocinclus spend a lot of their time feeding on algae and slime that builds up on rocks and plants. However, contrary to popular belief, these fish are not full herbivores. They will also eat tiny crustaceans, protozoa, and small pieces of flesh from animals and fish.
Also contrary to popular belief, you can’t just throw a group of six Otos in your tank and expect there to be enough algae to sustain them over time. In other words, you need to provide extra food. We recommend algae wafers or Catfish pellets.
To mix up their diet more, you can give them blanched vegetables such as:
- Brussel Sprouts
Weigh the veggies down using a Veggie-clip, plant weights, or a rubber band around the veggies and a small rock. This will keep them in place long enough so your bottom feeders can snack. Make sure you wash the veggies before adding them to the tank to remove any residual pesticides. And don’t leave them in the tank more than 3 days or else they will start breaking down and messing up your water parameters.
How Often Should I Feed my Oto Catfish?
Feed your Otos once or twice a day. You want to place their food in their territory so they can get to it easily. Feed no more than they can consume in about 10 minutes.
Oto Catfish Tank Mates
Oto catfish are friendly, peaceful fish. They’re typically great options for community tanks. The ideal tank mate for Otos won’t directly or aggressively compete for food, is peaceful, and thrives in the same water parameters. Here are a few types of fish that are excellent tank mate options:
- Corydoras Catfish (Cory Cats)
- Chili Rasbora
- Ghost Shrimp
- Vampire Shrimp
- Cherry Barbs
- Mollies, Guppies and Platies
- Neon Tetras
- Clown Pleco
However, this doesn’t mean you can pair Oto catfish with every single fish in your local pet store. These fish are definitely no-go’s as they will likely try to eat your little Otos:
Oto Catfish Breeding
Breeding Otos is not the easiest process. They’re very sensitive to water chemistry changes, which can make it difficult to get all conditions correct.
It is very likely that your Otos are wild-caught. This means there is a good chance a breeding pair will produce healthy offspring, and you won’t be subject to complications due to inbreeding.
We recommend keeping breeding pairs in a tank by themselves. Once the males start chasing a female around, partition off that female with one male. Otos don’t release a ton of eggs per cycle – only about 10 – but they can have multiple cycles per year.
From there, keep an eye on things to see when the female lays her eggs. In your breeding tank, you will want lots of moss where the eggs can mature safely.
It is not fully known if Otocinclus will eat their own eggs so to be safe, move the breeding pair out of the tank once the eggs are fertilized. This will give the eggs and fry a safe place to mature.
Once the eggs hatch and fry are swimming, feed them infusorans and algae. If you’re considering adding brine shrimp for the fry to eat, wait until the fish are at least 1/2 inch long.
If you are able to successfully breed Otos, you might be able to sell them to pet stores, including chains. Captive-bred Otos are hard to come by and typically have much better survival rates than their wild-caught counterparts.
How to Sex Oto Catfish
Otocinclus are pretty challenging to sex; the main visible difference is that females are usually larger and broader. This is most easily observed when viewing the fish from the top or bottom. From the side, it is usually difficult, if not impossible, to see width differences.
Oto Catfish FAQs
Are Oto Catfish aggressive?
Otos are peaceful and friendly fish. They’re small when full grown and tend to hang out in shoals with other Otos. Their main source of food is algae and vegetation. All of these reasons stack the Oto to be excellent community tank members.
Are Oto catfish Hardy?
Once Otos are acclimated and have a consistent and healthy source of food, they can be hardy and live for several years. However, the vast majority of them of wild-caught, which means that they go through a stressful trip where they’re not in ideal conditions before arriving at the local pet store. This means a lot of them die on arrival at the pet store, and then will often die unexplainedly in your tank within a few days of purchase. Because of this, we classify them as less hardy than some other species.
Do Otocinclus catfish need oxygen?
Similar to other suckermouth catfish, Otocinclus catfish can supplement the oxygen they get from their gills in the water with direct intakes of atmospheric air. Because of these dual capabilities, you might see your Oto taking breaths of air from the surface. If you see this very frequently, make sure you have sufficient oxygen because your other gill-only breathers might be struggling with low oxygen levels.
Are Oto catfish nocturnal?
No, Oto catfish are not nocturnal. Otos are active during regular daytime hours. They’ll typically be at the bottom of your tank, grazing on algae and vegetation. In an established, healthy tank, you will find them alternating algae-eating activities and brief rest stops in the tank’s hiding places.
Conclusion – Is the Oto Catfish a Good Fish for Me?
The otocinclus is a popular freshwater fish that can be found in aquariums across the world. These adorable little guys are often brought into aquariums for their appearance, algae-eating skills, and friendly demeanor!
They’re not too hard to care for if you know what you’re doing. We’ve covered everything you need to know about them from tank size requirements to feeding habits in this guide so we hope you feel confident in supporting your catfish. Why do you love Oto Catfish? Let us know with a comment below!