Purple firefish FAQ

by Owen James

The distinct pose adopted by every happy purple firefish you'll ever see

The distinct pose adopted by every happy purple firefish you'll ever see

The purple firefish has only been popular in the marine hobby for about 20 years, but in that time it’s become a very popular inhabitant of reef and more peaceful fish-only aquariums.

Purple firefish Frequently Asked Questions

Where does the purple firefish come from?

The purple firefish, Nemateleotris decora, hails like most tropical marine aquarium species from coral reef areas. They are found in a large range throughout the Western Indo-Pacific, specifically from Mauritius to Samoa, north to Ryukyu Islands, south to New Caledonia.

The purple firefish is collected in deeper water of 25-75m, which is doubtless why it took longer than other similar species to make it into the hobby.

Like many species of its shape, the purple firefish is designed to dart into small holes when alarmed, so it is usually found in rocky areas rich in crevices and holes.

How big do purple firefish grow?

These are small fishes that grow to 9cm, but usually a bit less.

Can I keep the purple firefish?

Purple firefish are fairly straightforward marine fish to keep, provided some basic needs are met:

  • Always cover the aquarium – purple firefish are notorious for jumping out of open-topped aquariums
  • Either keep one fish per tank, or better keep a small shoal in aquariums larger than 500 liters or so. Pairs are liable to fight, unless you can buy a mated pair; they are reportedly monogamous in the wild.
  • A well-decorated aquarium with lots of rocky nooks and crannies will encourage these fish to settle in and spend more time confidently holding position in the water column
  • A good current recreates their natural environment
  • Watch out for signs of aggression. The purple firefish is not a fish that will survive being bothered by aggressive species, yet it will also sometimes bully very shy species, especially other firefish.

In terms of tank water, the usual criteria apply: good clean water of the correct specific gravity, with zero ammonia and nitrite, and nitrate ideally less than 25ppm.

To whet your appetite, here’s a rather grainy video of a purple firefish living in an aquarium with a clownfish:

What do purple firefish eat?

In nature, firefish hover above the substrate and pick out zooplankton such as copepod larvae from the water currents.

A comparable diet in captivity is small, frequent feedings of tiny pieces of frozen food such as brine shrimp, mysis and krill. Try to accustom them to a daily feeding of a decent flake or pellet food, too, as this will help ensure they get all the nutrients they need.

Has the purple firefish been bred in captivity?

Yes, it has been spawned since the early 1990s, though not with any great regularity. Raising the young is another matter, however.

According to the purple firefish breeding entry on the MOFIB forums (which terms them ‘dartfish’):

For such a popular group of aquarium fish, surprisingly little information is available regarding their reproduction.

Reports on breeding almost seem like apparitions, everyone seems to know someone who’s “bred” their dartfish, yet no one has raised any, and the sparse details on observed reproductive behavior vary wildly from account to account.

Dartfish represent a great opportunity for those individuals who wish to try something different and make a valuable contribution of knowledge to the marine ornamental breeding community.

For a few more clues to breeding, read this purple firefish spawning report on the Breeder’s Registry.

Where can I learn more?

Have you kept them? Add to our knowledge in the comments below (keep to information about this fish species only, please).

Read the Ultimate Secrets To Saltwater Fish And Invertebrates.

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