Are Black widows a good first tetra to breed?

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Looking for a new breeding project? Dr Heok Hee Ng advises on breeding the Black widow tetra.

Black widow tetras (Gymnocorymbus ternetzi) are good if breeding tetras for the first time. They are relatively hardy and can tolerate a wide range of conditions, especially since those in the trade are commercially bred.  

Black widows are not too difficult to sex either, as the males are smaller and more slender than females, are darker and have a wider anal fin and a narrower dorsal fin.

A suitable breeding set-up should consist of several males and females, although it is possible to use only a pair. The breeding tank should be bare, with two or more spawning mops and a sponge filter.

Water conditions for breeding should be on the soft, acidic side (pH about 6.0, GH not more than 8) and temperatures around 24-26°C/75-79°F.  

Lighting should be subdued, and covering the sides and back of the tank helps. Prior to any spawning attempt, the fish should be conditioned with ample feeds of live and frozen food. Keep up with water changes to maintain quality.  

The fish should be monitored closely after being introduced to the breeding tank, as tetras are notorious egg eaters and parents must be removed as soon as spawning is complete, typically in the morning. Remove the spawning mops, shaking them to remove all eggs to the tank floor.

Tetra eggs are sensitive to light and the tank should be shielded for five to six days. The eggs typically hatch in about 24 hours, with the fry becoming free swimming after five or six days. Then they can be fed infusoria or similar fry food, graduating to brineshrimp nauplii after another 48 hours.

During this time, make frequent small water changes to maintain quality without creating drastic changes in conditions.

This article was first published in the December 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.