Siamese algae eater

Crossocheilus oblongus

FreshwaterFish

Care at a glance

Temperature: 68–79°F (20–26°C)
pH: 6.0–7.5
Adult size: 6.3 in (16 cm)
Minimum tank: 37 gal (140 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Bottom
Difficulty: Medium
Breeding: No record
Rarity: Common
Origin: Thailand, Malaysia
Family: Cyprinidae

Overview

These are bottom-oriented schooling fish, so keep a small group of five or more in a tank of at least 140 liters to allow for their adult size. They are peaceful and active and spend the day grazing surfaces. They eat algae, including black beard algae when young, but you must supplement with sinking pellets, wafers, and frozen food. They want clean, soft, slightly acidic water with steady flow.

In the wild

Siamese algae eaters come from fast, clear streams and flooded forests in Thailand and Malaysia. The water there is soft, slightly acidic, and well oxygenated over rocks and leaf litter. Match that with good flow, clean water, and a temperature in the low to mid-20s C. Smooth surfaces and driftwood give them places to graze.

Good to know

Crossocheilus oblongus is a cyprinid, related to barbs and danios. It grows larger than people expect, up to around 16 cm as an adult. It is widely sold but has no reliable record of breeding in home aquariums. Look for the clean black stripe running into the tail, which helps tell it apart from similar look-alikes.

Did you know

Young Siamese algae eaters are one of the few fish that will actually eat black beard algae, which is why they are popular with planted-tank keepers. As they grow, their appetite for it fades and they switch to easier prepared foods.