Otocinclus Catfish - Otto Cat

Scientific Name : Otocinclus sp., over 22 species known

Common Names : Otto, Oto Cat, Dwarf Sucking Catfish, Midget Sucker Fish

Care Level : Easy but needs to be slowly acclimated (preferrably drip acclimated) and you must keep them in optimum water conditions by performing frequent partial Water changes. Only add them to tanks that have completed the aquarium nitrogen cycle. They love heavily planted tanks!

Size : Up to 2 inches (5 cm)

pH : 6 - 7.5

Temperature : 70°F - 78°F (21°C - 26°C)

Water Hardness : 6° to 15° dH

Lifespan : 3 - 5 years

Origin / Habitat : South America in well oxygenated, moderate or slow flowing water where this is plenty of algae to eat.

Temperament / Behavior : This is a very peaceful catfish and does well when kept in small schools.

Breeding : They can be difficult to breed in the home aquarium. They will lay eggs on plant leaves.

More Breeding Info: (credit: Armadillo)

• They'll kind of 'smell' each other like dogs, and then the female will rest on a surface and the male will intertwine his body with hers. He's fertilising her eggs.
  
  
• She'll lay her eggs all around the tank, not in one big clump. The good eggs are transparent with a bit of dark inside, the bad eggs are fluffy white. Do get rid of the bad eggs with a turkey baster as they're covered in fungus which could be detrimental to the rest of the eggs.
  
  
• The male will defend the eggs, which is really cute. He just kinda stands watch around them.
  
  
• If you want oto fry, you'll need to get rid of any fish in the tank that could potentially eat the eggs of course
  
  
• After a couple of days, the eggs will disappear and you'll see some tiny wrigglers. If your wrigglers make it past a week, you have a good chance that they'll survive. The fry survival rate is really low.
  
  
• A week or so later, she may lay more eggs.
  
  
• The fry will eat the same as the parents (in my experience). I don't give them fry food as they'll not find it and it'll just pollute the tank
  
  

Aquarium Size : 20 gallon or larger.

Tank Mates : Many, given their peaceful nature. Avoid keeping with fish large enough to eat them and fish that are overly aggressive.

Disease : Freshwater Fish Disease - Quarantine all new fish before adding them to your aquarium!

Things To Watch For: Paleness. Paleness in an oto is a sign of stress. A lot of people report death within 24h of first noticing the discoloration. Stress can be caused by many factors including: excessive tank disturbance by humans, aggressive tank mates, not enough hiding places, not enough other otos, water parameters, temperature, etc. Buuuut, they are quite transparent fish, so if they are in brightly lit conditions against a white background, don't panick! Just look at them under normal conditions (natural light) to see if their stripe is nicely visible. If it is, then they're not alarmingly pale.

Sunken belly: it is imperative that they get a constant source of food. An oto with a sunken belly may already be on the way out.

Diet / Foods : Herbivores, you may need to supplement their diet with algae wafers. Here are some more good foods to use:

Hikari Algae Wafers
Nori Algae Sheets

More Food Notes: (credit: MamaM on the Fishlore forum)

• They need a really REGULAR food intake. Some can be condemned if they dont' get food in as little as 12 hours. Always leave food out for them if you're low on algae.
  
  
• They need a lot of algae, so do consider setting up an 'algae farm' outside in your garden, or close to a window. All it is is a clean fishbowl covered with a clear top (to let the light through on top as well), and you put a couple of (clean) glass jars in there to grow algae on. When your jars are covered in algae, you can drop them in the tank. After a while, you can rotate your algae-covered jars from outside with your algae-cleaned jars from inside.
  
  
• Do not forget to seed your algae farm with some waste matter by rinsing the filter in it. If you don't do it, algae take ages to grow. If you do do it, algae can grow in a couple of days but, don't overdo it or all your ornaments will be covered in algae.
  
  
• Always leave a long strip of cucumber or zucchini (give them as big a surface area of the vegetable as there is space for, so they find it easily). Do remove it after 24 hours or so to avoid a nitrate spike from the vegetable rotting. I pretty much constantly have a slice in the tank, and constantly have an oto on it! Buuut, it took a while for them to get it. (well, a while, a week or so I think).
  
  
• They're not averse to the odd algae wafer, although this shouldn't be their staple diet. In case they dont eat it, put it in a bowl inside the tank (not a plate, or it might fall in the substrate anyway). That way, if they don't eat the wafer after 24h, you can easily find and remove it (uneaten algae wafers can easily pollute the tank, sometimes causing nasty nitrate spikes).
  
  
• Some are not so good at locating their food, or identifying something as food. Don't despair and keep trying (e.g. with cucumbers) by putting large chunks of the food always in the same place. They'll eventually get it. I always add my algae wafers in a little plate they've got in the aquarium. Now they know to check the plate.
  
  
• I do add a frozen spinach leaf for something different (freeze the bag of baby spinach, then take one out and thaw a little and stick it in with a veggie clip to weigh it down... they LOVE it!)

Tank Region : Mostly middle to top.

Gender : The male is usually smaller than a female of the same age.

Fish Lore Forum : Otocinclus Catfish Forum

Photo Credit : Photos copyright JJPhoto.dk

Site References :
Fishbase
Wikipedia