Pygmy Otocinclus
Otocinclus macrospilus
A tiny peaceful algae-eater; keep a group in a mature, algae-rich tank.
| Difficulty | Intermediate |
| Min. Tank Size | 60 L |
| Temperature | 21.0–27.0 °C |
| pH Range | 6.0–7.5 |
| Max Size | 4.0 cm |
| Lifespan | 3-5 years |
| Diet | Herbivore |
| Temperament | Peaceful |
Overview
The Pygmy Otocinclus (Otocinclus macrospilus) is a tiny peaceful algae-eater; keep a group in a mature, algae-rich tank. It is a popular choice among Australian aquarists, reaching around 4 cm and living roughly 3-5 years when properly cared for.
This complete guide covers how to keep the Pygmy Otocinclus successfully - tank size and setup, water parameters, the best foods (including recommended brands), suitable tank mates, breeding, sexing and the health issues to watch for. It is rated Intermediate to care for.
Natural Habitat & Origin
This catfish comes from the rivers and streams of South America or Africa, foraging along the bottom for food. It appreciates hiding places, soft substrate and clean, well-oxygenated water.
Matching the temperature, water chemistry and cover a species evolved with is the simplest route to keeping it healthy and seeing its natural behaviour and colour.
Tank Size & Aquarium Setup
Provide a minimum of 60 litres for the Pygmy Otocinclus. As a group-living species, swimming length and floor space matter more than height.
Include driftwood and caves for shelter; wood aids digestion for many plecos and gives bottom-dwellers somewhere to feel safe by day.
Always add fish only to a fully cycled, mature tank with stable biological filtration. Match filtration generously to the fish's size and waste output.
Water Parameters
Keep the Pygmy Otocinclus in stable water at 21-27 °C with a pH of 6.0-7.5. It adapts to a moderate range, so stability matters more than an exact figure.
Test regularly: ammonia and nitrite must read zero, and nitrate should be kept low with routine partial water changes. Always dechlorinate and temperature-match new water, because sudden swings cause far more illness than water that is stable but slightly imperfect.
Diet & Feeding
The Pygmy Otocinclus is a herbivore and grazer that needs a plant- and algae-based diet rather than meaty foods it cannot fully digest.
In Australia, good options include Hikari Algae Wafers, API Algae Rounds and Dymax Spirulina wafers, plus blanched vegetables. Feed small amounts once or twice a day (only what is cleared in a minute or two), vary the diet for the best colour and health, and avoid overfeeding, which is the leading cause of poor water quality.
Temperament & Tank Mates
The Pygmy Otocinclus is peaceful and community-friendly. It mixes well with other calm species that share its temperature (21-27 °C) and pH (6.0-7.5) needs, are too large to be eaten and not large enough to eat it.
It is happiest in a group of its own kind and is shyer and less settled when kept alone.
Breeding
The Pygmy Otocinclus is an egg-scattering species. To breed it, condition a group on rich foods, then move them to a dim tank with fine-leaved plants or a spawning mop; the parents scatter eggs and will eat them, so remove the adults after spawning.
Even if you are not planning to breed it, recognising this behaviour helps you understand what you are seeing and respond well - for example by adding cover for fry or giving a guarding pair extra space.
How to Tell Males from Females
Females are generally rounder and fuller-bodied; in many Synodontis and similar catfish, visual sexing is difficult outside breeding condition.
Common Health Problems
Scaleless and fine-scaled fish like this react badly to poor water and to copper-based or full-dose medications, so treat at half strength. They are also among the first to show ich. Quarantine new arrivals for 2-4 weeks and watch daily for early signs such as loss of appetite, unusual hiding, clamped fins or laboured breathing - caught early, most issues are very treatable.
Prevention beats cure: keep water pristine, avoid overstocking and overfeeding, quarantine new arrivals, and act at the first sign of trouble.
Is the Pygmy Otocinclus Right for You?
The Pygmy Otocinclus suits keepers with some experience and a stable, mature, appropriately sized tank, as long as you can provide at least 60 litres, water at 21-27 °C and pH 6.0-7.5, the right diet and a proper group of its own kind.
Meet those needs and the Pygmy Otocinclus will reward you for around 3-5 years. Use our free aquarium calculators to plan your setup, and explore our other fish, plant and disease guides to build a thriving aquarium.
