Dwarf sucker – Otocinclus

Otocinclus are best known as algae eaters and they one of the best algae eaters around. It’s their natural food which makes them very easy to feed. They’re easy to look after too, so are great for beginners.  Adult size 5 cm, min tank size 40 litres.

Otocinclus is a genus of catfish in the family Loricariidae native to South America which are commonly called dwarf suckers or otos.  They are native to South America, mainly the rivers of North Argentina and Venezuela. Unusually for South American tropical fish, they are not found in the large Amazon River which runs through the continent.

They’re peaceful creatures and can be put in a variety of freshwater community aquariums.

They have a limited ability to breathe air. A duct between the esophagus and stomach forms a hollow area which lets them breath.

Behaviour

Otos are small and peaceful fish that try to stay out of the way. They could easily be eaten by larger fish so they are skittish by nature. You will see them dart across the tank when they get scared. They can move very fast, which doesn’t help when trying to catch them in a net!

Much of their life is spent at the bottom of the tank and on the surfaces of decorations, plants and aquarium walls. If there is no algae, they will move onto a new surface.

A group tends to stick together, grazing the same areas. When a group is latched onto the sides of the tank you’ll get an interesting view of their underside, revealing how they use their mouth to get a firm grip.

Tank Conditions

They are mostly found in small streams or shallow rivers across South America. Here they attach themselves to the substrate or rocks in the search of algae. The warm waters are slow-moving but well-oxygenated, pH is generally neutral. Below the water is a soft, sandy substrate. Perched on the substrate are pieces of debris like rocks, wood and anything else being moved with the water.

They’re bottom-dwelling fish so setting up the lower levels of the tank correctly is crucial. Pick a fine-grained sandy substrate; coarser grains can scratch their body and lead to health problems. Some plants are around, but not a lot of them. They have access to plenty of light and it penetrates through the shallow waters.

Pick some decorations and spread them across the substrate. Rocks can be used to create caves (these will be used as shelter when your Otos are stressed). Plants can be used to provide more shelter. They also provide more surfaces for algae growth too. Though they’re vegetarians, Otos will stick to algae instead of eating your plants.

You don’t need any special equipment to move the water. You could use a standard air pump for oxidation, but it’s not necessary. Standard aquarium lights will be fine too.

A 40 litre tank is suitable for for a small group (4-6) of Otos. Just make sure they can get enough algae to eat.

Compatibility

Otos are small and peaceful so won’t be an issue for any of your other fish – this means there are lots of possible tank mates.

Their small size makes them an easy target though, so large or aggressive fish need to be avoided. This means that a lot of cichlids aren’t a good pick. An Oscar could hunt down and kill an Otocinclus with ease. A general rule is to stay away from species with an aggressive reputation or a mouth big enough to eat an Oto whole.

This still leaves plenty of species to choose from. Some popular choices include Angelfish, Cherry Barbs, Corydoras Catfish, Danios, Dwarf Gourami, Guppies, Harlequin Rasbora, Mollies, Tetras, and Zebra Loaches.

Feeding

These fish are herbivores which restricts what you can give them but there are many fish foods for herbivores to choose from.  They mostly eat algae which is what they would normally eat in the wild. Despite them eating algae, you still need to add some other food too. The algae will run out quickly if you keep a large group of Otos.

You can feed them algae wafers and they should disappear over a few hours. Add one every couple of days.

Just be careful not to overfeed your Otos. It’s important to monitor algae levels in the tank and use this to decide how much supplementary food to give.

Care

A healthy tank usually means that you will have healthy Otocinclus, but they can be fragile fish. Sometimes individuals can die shortly after being introduced to a new aquarium, even if they look healthy and the tank’s conditions are perfect. Most will be fine though.

Otos aren’t prone to any particular diseases, but they can suffer from some parasitic and fungal problems that are common among freshwater fish, like Ich. See Fish Disease Diagnosis and Treatment at Rebel Pets for help with diagnosing and treating diseases.

The water in the tank needs to be nice and clean, with ammonia and nitrite levels staying at 0ppm. Water changes every 1-2 weeks will help with this. When cleaning the tank, perform water changes to reduce pollutants but don’t completely wipe away all the algae you see.