Fathead minnow, Pimephales promelas


The North American Fathead minnow, Pimephales promelas, is a really interesting little fish for the coldwater aquarium and has fascinating breeding behaviour, as Jeremy Gay explains.

Scientific name: Pimephales promelas.

Common name: Rosy red minnow, Fathead minnow.

Origin: Canada and North America, to Mexico.

Size: Up to 10cm/4” for males. Females at 5-7.5cm/2-3”.

Diet: In the wild feeding on detritus, algae, copepods and aquatic crustaceans — in the aquarium taking flake and dry foods frozen and live.

Water: From 10-20°C/50-68°F is ideal, though will tolerate temperatures cooler and hotter.

Notes: Rosy reds have fluctuated in availability, probably because retailers and suppliers are unclear as to their legal status in the UK.

They are noted for tolerating low oxygen and turbid water conditions other fish cannot.

The red coloration was discovered on a US fish farm and then line bred. Natural Rosy reds, or Fathead minnows, are grey/brown with dark patches and a feint horizontal stripe from head to tail.

Rosy reds lay eggs and guard them much like a cichlid. They use caves or the underside of lily pads and can be bred easily in the home aquarium.

Aquarium: As active, shoaling fish we recommend a minimum tank length of 90cm/36” and around 100 l/22 gal in volume. Keep on their own or with other temperate, similarly-shaped fish like Red shiners or danios. They are best not mixed with goldfish.

Sexing: Males develop a fatty growth on the head, hence Fathead minnow. They also develop pronounced tubercles on their heads at spawning time and naturally coloured males develop vertical stripes at the same time.

Identification: As we only see the red form in the UK they are fairly easy to identify — and other members of the Pimephales genus are not available. They may be mistaken for young Golden orfe, though Rosy reds have a shorter head profile.

Availability: In several UK retail outlets in the summer of 2009 and most shops should be able to order them in.

Do you need a licence? Defra state: “Rosy red minnows are a non-native species, the keeping of which is regulated under the Import of Live Fish Act (1980). To prevent the potential spread of this species to the wild, those wishing to keep or sell these animals must be licensed.”

Wholesalers and retailers must have individual licenses for their premises. Wholesalers must also record which retailers they supply and the number of the fish supplied in each batch. Retailers must keep records of the number of fish received and sold.

A general licence allows Rosy red minnows to be held in indoor aquaria for ornamental purposes.

Hobbyists can hold them in their tanks without requiring an individual licence, but they must not introduce them to garden ponds or allow them to escape into the wild.

Price: About £2.00 each specimen.

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