What temperature should my water be for Gastromyzon loaches? Heiko Bleher explains...
Gastromyzon are endemic to Borneo, a tropical island which has a high mountain range. Being tropical, temperatures never drop very low, except on the top of the highest peaks where no fish live.
To my record Gastromyzon bario is the highest living species, and I collected it in Sungai Padapur, in north Sarawak, at 1150m/3500’. Minimum temperature was 15°C/59°F, normally higher.
G. monticola, from the lower reaches of Mount Kina-Balou (4101m) was found at similar temperatures. All others are from lower reaches like G. ingeri which occurs up to 270m in the Tawau River, in Shaba, also Malaysia, lowest temperatures between 18-20°C/64-68°F.
The other 29 species (32 are considered valid) live mostly in forest streams in the lower reaches and in the valleys where temperatures hardly ever drop to 20°C/68°F and as good as never below.
As a rule of thumb temperatures should not drop below 20°C/68°F or exceed 27°C/81°F and average around 24-25°C/75-77°F.
The recently described species Neogastromyzon kottelati comes from a stream feeding the lake Danau Sentarum, and prefers water 2-3°C warmer. But Neogastromyzon crassiobex and N. chini are found at 24-25°C/75-77°F.
A species I found many years ago in Brunei Darussalam in the Temburong River basin and recently described as Gastromyzon cranbrooki, lives in warmer habitats of 25-27°C/77-81°F. I even measured 28.5°C/83°F.
There are a few things to consider for these loaches. They need a rocky habitat, with sand, gravel and rounded stones. The tank should have a swift current (from 0.65-3.7 m3 per second).
Hardness should be less than 2°GH and the oxygen level should be at least 7.5mg/l. They should be kept in shallow tanks as they’re found in streams with a gradient of 20%. They won’t need a heater if your home stays above 20°C/68°F all year.
This item was first published in the November 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.