Tim's Tropical Fish







Otocinclus affinis

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Otto Otocinclus affinis

The Otto originates from southeastern Brazil.  It is also known as the Golden Otocinclus, the Dwarf Suckermouth, the Pygmy Suckermouth and the Midget Suckermouth Catfish.  The scientific species names for the Otto include Otocinclus affinis and Otocinclus vittatus.  The body shape and coloring are similar to a Flying Fox and a Chinese Algae Eater.  There is a dark, black mottled band running from its head into its tail fin. Below the banding it is silvery white.  Above the banding it is brown in a mottled pattern. Water conditions should be very clean.

The Otto is the perfect algae eater.  It eats soft algae exclusively, so make sure a food supply is established in the tank before an Otto is introduced.  It will clean algae off of plants without harming the plant.  It also will clean algae off of plastic plants and glass.  Ottos are seldom active in a tank, but they are always entertaining to find.  They will stick themselves to the glass in any direction.  They will stick to plant stems and the underside of leaves.  Occasionally they will swim across the tank to take up a new resting or eating position.  Ottos won't harm other species and the only concern is that some larger, aggressive fish, such as cichlids, will eat them.

Although the literature indicates they should be kept in groups of three or more, I had a lone Otto for years and "Norbert" was always a source of pleasure and a challenge to find.  "He" went through lots of tank mates without paying any attention to them and was impervious to disease.  Best of all, he loved algae all his life!

Differentiating the sexes of Ottos and breeding them is very difficult.

Otto Otocinclus affinis

Comments by LittleHippyGirl: Ottos are cute little critters If you have room, get more than one because they feel MUCH more secure in groups. They only eat soft green and brown algae, nothing else. Most ottos in pet stores are underfed, so a tank full of yummy algae would be heaven for a new oto. They can be shy, so the best set up would be to have live plants. If you don't want live, make sure there are plenty of broad-leaved silk plants for them. In my experience, ottos aren't too fond of bare bottomed tanks (my quarantine tank is bare bottom) so make sure you have gravel. They stay under 1.5" so make sure no tank mate is big enough or will be big enough to eat them. They have spiny fins so if the otto is swallowed, you will most likely end up with 2 dead fish.

Ottos are adaptable to a wide range of pH and water hardness, but adapting is the hard part. They are usually more weak and stressed than most fish, and some usually die within the first couple weeks of home-bringing. It is extremely important to make the trip home as quick as possible, and acclimate them very slowly to the new pH of your tank. Make sure their water is free of poisonous ammonia and nitrite. I am happy to say that I had a 0% mortality rate with ottos! This is odd and frankly I was expecting the two I bought a few months ago not to make it because many of the fish I bring home are sick or overly stressed at the pet store, and they only other 0% is bettas. Anyways, if they are strong enough to adapt to your water and live past 2 weeks in their new tank, you will likely never have any problems with them.

Advice on Buying Otocinclus by Bernie:

  • Never add them to a tank that hasn't been established for at least 6 mths.
  • Wait until they have been in the LFS for a few weeks before buying them and make sure there stomach is nice and round.
  • Avoid any fluctuations in any water parameters. As well as the normal ammonia/nitrite, they seem particularly sensitive to PH and nitrate fluctuations for some reason. Always try to keep nitrate below 10.
  • Keep dissolved oxygen levels up and have a relatively strong water current.
  • Try and have brown algae (diatoms) present in the tank, particularly when the otos are introduced, it is a great food source for them and it is their favourite.

Some say that otos should only be kept in a planted tank (due to the plants aiding in better water quality and they also provide a bit of extra food if the algae is scarce, but I have had my guys for a long long time now and they are doing very well in my tanks that are all unplanted. It may come down to just the luck of the draw sometimes with these fish.

Scientific Name: Otocinclus affinis
Family: Catfish
Temperature: 20 - 26 C; 68 - 79 F
pH: 6.0 - 8.0
Size: 4 cm; 1.5 inches
Life Span: 7 years
Breeding: Difficult, Egglayer


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