Purple Firefish Care Guide

Alison Page

Alison Page


Purple Firefish

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If you own a marine tank, there is a dazzling array of colorful fish and invertebrate species to choose from as its inhabitants. One of our favorite fish, The Purple Firefish, is a fabulously colorful and beautiful addition to any tank. This reef tank fish is hardy and beginner-friendly, so those new to the marine fish-keeping hobby can confidently buy one of these beauties. 

Read the guide below to learn how to care for these stunning little bottom-dwelling fish.

Background and Origins

The Purple Firefish is a saltwater fish species also known as the Purple Dartfish, Decorated Dartfish, Flame Firefish, and Elegant Firefish. The fish’s correct scientific name is Nemateleotris decora

The Purple Firefish belongs to the Gobiidae family and is a species of dartfish closely related to gobies.

These fish live in the tropical Indo-West Pacific Ocean area, specifically around Samoa, Mauritius, the Ryukyu Islands below Japan, and other nearby locations. In these regions, the water is typically warm and alkaline. 

The shy fish lives a solitary life, inhabiting the lower areas of reefs at depths of up to 230 feet, hovering around the coral rubble and sand substrate in deep waters. The habitat offers plenty of protection and refuge from aggressive or predatory fish. Water conditions at the bottom of reef drop-offs tend to be unstable, and strong currents can buffet fish at times.

Purple Firefish are relatively easy to care for beginner species and make an excellent addition to a small reef tank setup.


Purple Firefish are generally readily available at good marine fish stores and online.

Prices for individual fish vary widely, depending on the size and age of the fish and the store’s location. Generally, you should expect to pay from $30 to $60 for one fish. Remember, if you buy your fish online, you will probably have to pay for shipping, which adds to the cost of the fish.

How Long Do Purple Firefish Live?

If you provide your Elegant Firefish with the proper care and a high-quality, varied diet, you can expect your new acquisition to enjoy a usual lifespan of around three years. That said, some of these beautiful fish live longer than that.

Typical Purple Firefish Natural Behavior

This species of dartfish tends to hang around in the lower areas of the water column, keeping to itself and spending most of its life foraging for food. If the fish become stressed, they often hide in caves until the source of their distress has gone.

Although Purple Firefish are generally peaceful and non-aggressive toward other fish species, they can be very belligerent with their own kind. For that reason, we advise that you only keep one of these reef fish in your tank. Some owners like to keep a pair of Purple Firefish, but that can end in disaster, too. In fact, this species is primarily solitary in the wild environment, coming together only briefly to mate.

The Nemateleotris decora is reef-safe, and these amazing fish won’t hassle or damage your corals.

What Do Purple Firefish Look Like?

Although they share the common name of Purple Firefish, they display a plethora of dazzling colors, bringing your aquarium to life as they dart around.

The skittish fish are long and slender with mostly white body color. The fish’s anal and dorsal fins are short, with the anal fin extended right across the rear portion of the fish’s body. Their coloration varies from cool blues and purples to warm oranges and reds, typically with horizontal striping in a glorious gradient color scheme across the fins. On their heads, you can find shades of yellow and purple surrounding solid black eyes.

The Purple Firefish usually carries its long, narrow dorsal fin flat, although it might occasionally hold it erect. 

Gender Differentiation

Unfortunately, it’s pretty much impossible to tell the difference between male and female Purple Firefish — a frustrating detail if you want to try to breed them.

How Big Are Purple Firefish?

A fully-grown Purple Firefish can reach around 4 inches in length, making them suitable for life in a small reef tank.

Purple Firefish Care Guide

This guide section explains how to care for the beautiful Purple Firefish. As with most fish species, the best way to ensure that your fish remain healthy and long-lived is to provide them with an ideal habitat that replicates their wild environment as closely as possible.

What Size Tank For Purple Firefish?

Since the Purple Firefish only gets to measure around 4 inches long, you can keep them in a small saltwater aquarium of about 10 gallons or larger

Generally, the more space you can provide for these active fish, the happier they will be, especially living in a community tank. If you have a particularly large tank, you might be able to keep multiple Purple Firefish, as each individual can create its own territory and keep away from the others. However, there will always be the risk of an issue with Firefish unless each has plenty of space to occupy and claim as its own.

Whatever size tank you choose, make sure that it has a tight-fitting lid. After all, these fish can jump!

Tank Decoration

When choosing a substrate for your tank, we recommend that you go for a fine-grained, sandy material. Since Purple Firefish spend much of their time around the bottom of the aquarium, coarse gravel or coral presents a risk of injury to your fish.

Live rocks and corals make a nice inclusion for a tank that houses reef-safe Firefish. Be sure to include plenty of caves and hiding spaces, especially if you’re planning on introducing multiple fish to a large tank.

Water Parameters

To keep your fish healthy, you must maintain the correct water parameters for marine species. In the case of Purple Firefish, those parameters should be:

  • Temperature – 72°F-80°F
  • pH in the range of 8.1 to 8.4
  • Specific gravity – 1.020 to 1.025


These fish do fine under standard aquarium lighting. Fish don’t need light to thrive, but your corals do. So use whatever lighting system best suits the other residents in the tank.


Just like all fish species, Purple Firefish need clean water to thrive — meaning you need an efficient filtration system in your fish tank. 

This beautiful species is accustomed to a reasonably strong flow in their wild environment, so you need to choose a system that provides that.

Tank Maintenance

You’ll need to make partial water changes to keep water in the tank clean and remove nitrates. Also, you need to remove and wash the filter media once a month or so and replace spent media in line with the manufacturer’s recommendations.

Tank Mates For Purple Firefish

As previously mentioned, Purple Firefish can be aggressive toward their own kind, although they are generally peaceful with other species, including invertebrates and corals.

For that reason, we recommend that you only keep one Purple Firefish in a small setup or possibly in pairs in a large tank with plenty of hiding places. 

Suitable Tank Mates

Luckily, the Purple Firefish gets along well with most popular, peaceful marine species. However, some hobbyists have reported that they can be aggressive fish when it comes to other species of dartfish. Because of this, we recommend that you only keep one dartfish in the tank.

The best tank mates for your Purple Firefish are species of a similar size that won’t hassle them. A few examples of suitable tank mates for Nemateleotris decora include the following:

Purple Firefish also get along fine with invertebrate species, such as shrimp and snails, and won’t harm corals or sponges.

Purple Firefish Diet

Purple Firefish are primarily carnivorous, eating zooplankton and copepods in the wild environment.

To boost your fish’s colors, you might want to consider adding some supplements to the Purple Firefish diet. They typically eat whatever they find hanging suspended in the aquarium’s water column, including high-quality aquarium fish food flakes and frozen fish foods. You can also include small meaty food items, including brine shrimp, Mysis shrimp, and finely chopped crustacean or mollusk meat.

As a general rule, if you feed your fish a high-quality, varied diet,  they will enjoy excellent health and display their most vivid colors. 

How Much And How Often To Feed

Ideally, you want to feed your Purple Firefish two or three times a day, offering only what the fish will eat in a few minutes. 

Don’t overfeed the fish, as that can cause health problems. And putting too much food into the tank causes it to decompose, polluting the water and endangering your livestock.

Health And Disease

Purple Firefish are hardy fish and don’t generally suffer from disease. That said, you must keep your aquarium clean and remember to carry out weekly partial water changes. 

The most common disease plaguing Purple Firefish is Ich or White Spot Disease, which is caused by a parasite that infects the fish’s skin. 

At first, infected fish might flash or rub against objects within the tank and dart down the substrate to “scratch” their skin in response to the irritation that the parasites cause. As the disease progresses, a rash of tiny white dots like grains of salt appears on the fish’s body, head, fins, and gill covers.

To get rid of the parasites, we recommend that you treat the whole tank with an over-the-counter Ich treatment, following the manufacturer’s instructions carefully. In addition, raising the water temperature a few degrees for three days disrupts the parasites’ lifecycle. In just a short time, the disease should pass. Once the course of treatment is complete, be sure to carry out a partial water change.

Can You Breed Purple Firefish In Your Home Aquarium?

Although it’s difficult, you can breed Purple Firefish in your home fish tank.

Your first problem will be obtaining a male and a female fish. Males and females are almost impossible to tell apart, but you obviously need one of each sex to breed them successfully. The best way to get a breeding pair is to buy an already established couple from a fish store.

Set Up A Breeding Tank

For the fish to mate, conditions in the tank need to perfectly replicate the conditions they would experience during a breeding season in the wild. Keep the environment stable and provide the fish with a consistent feeding schedule, too.


Gradually increase the water temperature to 80°F to trigger spawning. Unfortunately, there’s no quick way to persuade the fish to breed. In some instances, it can take up to six months’ time for them to finally do the deed. 

However, once they eventually spawn, they will produce between 400 and 500 eggs, each of which takes about four days to hatch, releasing hundreds of fry. The fry is tiny, so we suggest feeding them on infusoria for the first week or two until they are large enough to take zooplankton and similar foods.

The parent fish will guard the eggs and fry, caring for them until the juvenile fish are large enough to be independent, usually about a month.

Is The Purple Firefish Suitable For Your Aquarium?

The Purple Firefish is a relatively low-cost marine fish whose beautiful, vibrant colors give you plenty of bang for your buck. These charming fish are sturdy and easy to care for, and they can live in a small tank of 10 gallons, making them the perfect choice for anyone new to the hobby.

Purple Firefish are peaceful with most other marine fish of a similar size, spending much of their lives foraging for food around the bottom of the tank and in the lower regions of the water column. That said, you can’t keep more than one Purple Firefish in a small tank, as they become aggressive toward their own kind and other dartfish.

Although it is possible to breed Nemateleotris decora in the home aquarium, it presents its fair share of challenges.

Overall, though, we thoroughly recommend these fantastic fish for beginners to marine fish-keeping.

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