Otocinclus (Otocinclus sp.) is a type of freshwater catfish that is commonly known as Oto Catfish. In recent years they have become one of the most popular algae-eating fish among aquarium owners. Their unique appearance and size make them a perfect fit for most aquariums. This beautiful fish will bring beauty and functionality to your aquarium.
This article will cover all the basics of Otocinclus care and everything else you need to know about this fish.
Otocinclus is a type of catfish belonging to the Loricariidae family native to the Amazon river in South America. They are commonly known as “dwarf suckers”, “Otos”, or “Oto Catfish”. This fish, like other loricariids, is a type of suckermouth fish and mainly feeds on algae and vegetables.
Otocinclus is a peaceful catfish that tend to be compatible with many other tropical freshwater fish and will make a great addition to any aquarium. They are easy to care for and can live in most aquariums.
In the wild, this fish lives in rivers and streams filled with driftwood and fallen trees that they can scavenge on them for food. They use these fallen trees to hide, eat, and breed. These fish are heavy algae eaters and will forge in the water for a perfect hiding spot that will also provide them with enough algae, vegetables, and insect larvae to feed on.
In your Aquarium, you will need to add driftwood, plants, and enough hiding spots for them to feel safe. They need a diet of algae, vegetables, and crustaceans to make sure they live a healthy life in your aquarium.
Their behavior is something that any aquarist can appreciate. Not only are they fun to watch, move around, and nibble on algae, but they get along well with a lot of other species. They are very peaceful fish and will not harm other fish, plants, or invertebrates.
This fish is mostly covered in darker green color on the back and yellowish-white color on the belly. They have a small cylinder body shape that will only grow to 1 – 2 inches. Depending on the type of the Otocinclus, the size, and colors on their body might be slightly different.
They are more colorful and vibrant when they are not under stress and might lose colors when water conditions are not in their favor. However, in captivity, they seem to hold on to their colors and patterns even when they are mature.
This fish has an armored back that feels boney when touched. Their belly is very soft and fragile, this is why they rarely swim in the water column to avoid exposing their soft spots to predatory fish.
Under the right conditions, Oto Catfish lifespan is about 3-5 years. When water parameters and diet are not in their favor they will live a shorter life. A bad diet, low water quality, and stress will reduce the life expectancy of this beautiful fish.
Otocinclus is one of the smallest catfish in the aquarium hobby. They will only grow to only 1 – 2 inches (2.5 – 5 cm) in size. This makes them an ideal fish for most tank sizes and you will not have to worry about the fish outgrowing your tank.
Behavior & Temperament
Otocinclus are active and peaceful fish that don’t mind living with other types of fish. They prefer to swim at the bottom or sides of the tank without causing any trouble for other fish or plants.
These fish are schooling fish and will live in large colonies in the wild. In your aquarium, you will need to have at least 6-10 of them so they feel safe. They will not fight with each other or other bottom dweller fish for territory.
They prefer to live in well-aerated tropical water temperatures with slow water flow. It is best to make your aquarium setup as close to what Oto Catfish get in nature as possible. To make this happen, you should place lots of plants, driftwood, and rocks in your tank. Algae and biofilm grown on driftwood and plants will provide them with a good source of food.
Most beginner fishkeepers buy these fish as algae eaters and think just algae in the tank is enough for them. While they are mainly eating algae in the tank, your tank does not provide enough algae for these guys to survive. Algae alone is also not a sustainable food source so you will need to provide them a proper diet. (more on this in Diet & Feeding section)
Overall, this is an easy-to-care fish and can tolerate a wide range of water parameters.
The minimum tank size for a small group of Otocinclus fish is 20 gallons. You might think this is a very small fish and can go in smaller tanks. Well, that might sound right at first but these fish are schooling fish and you need to have a group of 6 – 10 or even more. So they might not be a good option for tanks smaller than 20 gallons.
We recommend having bigger groups of Otos in your tank so you can see true schooling behavior in your tank. Larger groups will make the fish feel safe and will reduce stress levels. This means your fish will live longer and will live a healthier life.
Otos are relatively affordable fish to buy and getting a big group will not cost you a fortune.
These fish are not so fussy and will adapt to any tank setup as long as the water parameters are in their favor. You’ll find your Otocinclus thrive when you mimic its natural environment where they get a lot of driftwoods, plants, rocks, and sandy substrate.
Driftwood and rockets will provide hiding spots for the fish and make them feel safe and will reduce their stress levels. Sand is the best substrate for these fish because they have a soft belly.
Otos are herbivorous fish but will not cause any harm to live plants. Adding live plants will provide beauty to your tank and these fish will enjoy swimming around and hiding in the plants. Plants will make your fish feel less stressed.
Otocinclus need clean water so a good well-established tank is recommended. When filtration of your tank can not keep the water in pristine conditions it might cause health issues for this fish. Your fish might get internal or external infections or diseases, or even die.
These fish like to have a slow current in the rank so you will need to buy a filter that is not too strong. A simple sponge filter is the ideal filtration system for them. Tho most might not like the appearance of the sponge filter. You can also use hang-on back filters or canister filters.
A hang-on back filter or canister filter is the best option if you control the flow. You can simply place the out of the filter to a corner close to the sides so the sides break the force of the water coming out. This way you keep your tank super clean while providing your fish their ideal current.
These fish enjoy well-oxygenated tropical temperature water with a slow current in the tank. An air stone bubbler is highly recommended to increase the oxygen levels in the water.
Constant water parameters in your tank are the key to the health of Otos. Avoid fluctuating parameters in the tank. The following is the range this fish can handle.
- Water temperature: 72°F – 80°F
- pH levels: 6.5 to 7.5
- Water hardness: 7–15 dGH
Otocinclus Diseases & Prevention:
Otocinclus are hardy fish and do not get sick very easily. When water parameters are not in favor of this fish or they are under stress they tend to get sick. They are also susceptible to all common aquarium diseases that other fish might carry.
Prevention is the best cure! Never add new fish to your tank without properly quarantining them. Remind yourself to clean the tank regularly and keep an eye on the water parameters. Regular water changes and good food will prevent many of the diseases aquarium fish might get.
Diet and Feeding Requirements
Oto catfish are herbivorous (plant eaters) and need a diet consisting of algae, plant matter, fresh vegetables, and small microorganisms. Algae is the main part of their diet, but they will also eat fresh vegetables, small crustaceans, and insect larvae.
Algae is also one of the main food sources they have in the wild. You can easily supplement algae by feeding them algae wafers. Fresh vegetable and algae wafers should be the main food source they get with occasional meaty frozen food.
Some also try to feed Otos by growing natural algae in their tanks. To do this they simply increase the light duration in your tank. If this is the root you want to take, make sure you find the right light balance. You don’t want to have more algae in your tank than what your fish can consume.
You can feed Zucchini, cucumber, and other fresh vegetables with occasional frozen foods like bloodworm and brine shrimp. Just make sure you don’t feed them too much meaty food.
Males and females Otocinclus look very similar and are almost identical. Both genders are almost the same size and have the same color patterns.
The best way to get males and females is by buying a large group of them altogether. When selecting your fish in the pet store, buy some of the large ones and some of the small ones.
Females are slightly larger and bold than males. This is more obvious when they carry eggs in their bellies. This is more visible if you look at your fish from a top angle.
Fish behavior is also another way to identify males and females. Mature males usually swim around the fertile females in the group. If you see smaller fish chasing a larger fish then it’s a good indication that the smaller ones are males and the bigger one is female.
Breeding And Reproduction:
Almost all the Oto catfish sold in pet stores are wild-caught. This is because breeding this fish in captivity is not financially viable. This fish is easy to source from the Amazon River and is not in danger which makes it a relatively cheaper fish.
Breeding Otocinclus is easy and can be done in an aquarium. Otocinclus reach sexual maturity at about 9 – 10 months old. You will need a mature group with at least one male and a female.
When the female is ready to breed, you will see more round and full of eggs. The males will keep chasing her in the tank to fertilize her eggs. Then she will choose a place to lay her eggs and the male will fertilize the eggs. They usually lay eggs on plants or driftwood so make sure you have enough of both.
As mentioned above, the ideal tank for any fish is a tank that is as close to the fish’s natural environment as possible. This is super important if you want to breed fish. Most fish will live in different tank parameters but will only breed when they are in their optimal tank parameters.
In order to breed Oto cats successfully, you will need to follow the recommendations, we made in the “Tank Setup” section of this article. Doing this will give you a good ground in breeding them and once they reach maturity they will breed without you trying hard to make them breed.
Providing good high-protein foods during the breeding season will help the females to develop more eggs and breed faster. Plants are super important as they seem to only breed when enough plants are available in the tank.
Raising fry is easy as Oto catfish fry will feed on bacteria and algae already available in the tank.
Otocinclus Tank Mates
Otocinclus catfish are very peaceful fish and will not harm other fish and plants. They can live with any peaceful but not aggressive fish. Otos are very small fish this makes them an easy target for larger or aggressive fish.
They do well with other small non-aggressive fish in a community tank. Here are some of the compatible:
Are Otocinclus Right for You?
If you have an algae problem in your tank and your tank can house a group of 6 or more of these fish. Then we highly recommend getting these fish. These fish are very small and one of the best algae cleaning crews available in the aquarium trade. They will stay small and will not outgrow your tank.
In a community tank, they will need a 20-gallon or bigger aquarium. If you have a smaller aquarium that is already filled with other fish then Otos are not the fish you want to bring home. Otocinclus are kept in groups and the lowest we recommend is 6 or more otos in a tank.
Otocinclus is a dwarf catfish that looks beautiful and will not outgrow your tank. They are easy to keep and do not require a lot of maintenance. They are one of the best algae eaters available which makes them an ideal tank mate for planted tanks.
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