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Otocinclus Arnoldi

$10.95$19.95 ea.

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Otocinclus Arnoldi, or as they are also called Otos, Otto Cats, and Ottos. They may be the best scavengers that exist for freshwater aquariums! These little guys eat algae just like our Siamese Algae Eaters, so both are very popular for tackling an annoying algae problem before it gets out of control.

The Otocinclus Arnoldi is a small freshwater fish that can grow about 3 – 4.5cm when fully mature. These quick and agile swimmers can dart from one end of the tank to another in an instant, making them ideal for smaller aquariums or tanks with slower moving inhabitants.


Otocinclus In The Wild


Otos are native to South America and can be found east of the Andes throughout the lowlands from northern Venezuela to northern Argentina. They spend most of their time in schools, swimming through moderate-to-slow rivers with well oxygenated water.


Buying Healthy Otos


Otos are a great addition to any tank, but they’re very fragile initially. We have kept Otos as a specialty for many years, and we make sure they are sent to you nice, fat, and healthy – simply ensure you have a cycled tank, and all should be well.


Oto Behavior


If you keep your Otos properly, they’ll show a ton of activity and personality during the day. They’re diligent workers that will spend most of their time sucking on rocks, leaves with algae growing or anything else in sight!

It doesn’t matter which species of Otocinclus you own, they all require the same water conditions – low stock density and pristine water.


Otocinclus Aquarium


You’ll need an aquarium filter capable of cycling at least four times per hour (GPH) and with mature nitrate levels between 0-20ppm

No measurable ammonia or nitrite should be present either. 

Otos prefer water with a stable pH that is slightly acidic (6-7.5). 

The temperature inside their tanks should average about 22°C – 28°C degrees Celcius, allowing them to thrive year round without sustaining damage from changes in heat level outside. 


Tank Mates


Otocinclus Arnoldi is known for being non-aggressive by nature. If you choose tank mates wisely, then your Otos will be just fine!

These fish are great tank mates:

  • Neon Tetras.
  • Rasbora.
  • Cory cats.
  • Dwarf Gouramis.


Feeding your Oto 


Algae is the main food for Otos, but many aquariums can’t produce enough to sustain them. If you suspect this is the case, use algae wafers or Catfish pellets as a supplement.

The following are signs your Oto is hungry.

  • Your fish is digging around the substrate more than usual.
  • Noticeable size changes.
  • Sluggish behavior.


Breeding Otos


Otos can be hard to sex because you can’t see a difference. But, female Otos tend to be larger and wider than males if you look closely enough.

Otocinclus are not overly eager to breed. A high protein diet can get your Otos going. Brine shrimp and algae wafers have plenty of protein in them.

3.5/5 (90 Reviews)
Weight 1 kg

1 to 2, 10 or more, 3 to 9

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