Forktail Rainbowfish 101 (Pseudomugil furcatus)

Forktail Rainbowfish are one of the most underrated and beautiful freshwater fish out there. It blows our mind that so many aquarists know nothing about them!

These fish are peaceful, easy to care for, and stunning to look at. In fact, they might be one of our favorites!

But due to their lack of popularity, many people don’t know how to care for this species. This leads to unhappy and unhealthy fish.

Don’t worry though, this guide has you covered. It will teach you all the fundamentals of Forktail Rainbowfish care so you can purchase some with confidence!

Species Summary

The Forktail Rainbowfish (Pseudomugil furcatus) is a lesser-known freshwater species with a lot to offer.

Also known as the Forktail Blue Eye, it has a vibrant and colorful appearance that stands out in a natural backdrop. Pair that with its distinct fin shapes and you have a fish that’s sure to turn heads in your tank.

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One Forktail Blue Eye Rainbowfish near the substrate

Geographically, the wild distribution of the Forktail Rainbowfish is relatively small. They come from rivers in the Milne Bay Province in Papua New Guinea.

Luckily, this species breeds frequently in captivity. Thus, they are available from specialty breeders aquarium shops all over the world.

Playful by nature, Forktail Rainbowfish are known for creating a stunning display of color in a home aquarium. They’re a joy to care for and are easy enough for even novice fish enthusiasts to raise.


Even with superior care, the average lifespan of a Forktail Rainbowfish is around three years at most. This is actually not very long and often surprises prospective owners. 

In substandard living conditions, their life expectancy is even shorter. Like any captive fish, Forktail Rainbowfish need high-quality water conditions and a good diet. Without good care, these fish will experience health complications and short overall lifespans.


The Forktail Rainbowfish is one of the most visually unique fishes in the trade. Despite its small size, there are a lot of distinct physical details worth mentioning.

Let’s start with the shape.

The fish has a relatively simple torpedo-shaped body. The head is rounded and capped off with a superior mouth, which is oriented upwards.

The fins are what makes the shape of the Forktail Rainbow different. The spiny dorsal fin is small and subdued. However, it’s accompanied by a larger soft dorsal fin. It’s squared off and stretches towards the tailfin.

A similarly shaped anal fin is located on the bottom of the fish’s body. As for the pectoral fins, they’re upturned. The fins create a wing-like effect that’s very different from what you may be used to seeing with freshwater fish.

A Forktail Rainbowfish swimming in a planted aquarium

The Forktail Rainbowfish is an extremely colorful fish too! The main body color is silver-gray with a greenish tint. Accents of bright yellow are located all over the body.

You can find the color on the top and bottom of the fish as well as on the edges of the fins. Subtle black stripes accompany the yellow. The final signature detail of the Forktail Rainbowfish is its bright blue eyes!

Author Note: This species is sexually dimorphic. Males tend to be more vibrant in color. The fins are generally longer as well. Females may lack the wing-like shape of the pectoral fins.

Average Size

The average size of a Forktail Rainbowfish is only around two inches in length. This isn’t very big at all, and even the largest specimens will max out at around 2.3 inches.

In our opinion, this small size really goes well with their color. When you see these tiny creatures swimming around it creates a very dazzling effect!

Forktail Rainbowfish Care

If you’re looking for a fish species that’s easy to keep, this freshwater fish is definitely worth considering! Part of the reason why Forktail Rainbowfish care is so simple is the fact that this is a highly adaptable species that fare well in a wide range of conditions. 

In fact, they do very well in captivity and can even cohabitate with numerous other species (more on that a bit later).

That said, there are some care requirements you need to know. To help these fish reach their full potential in your tank, you’ll need to meet their basic needs!

Here are some established care guidelines you should follow.

Tank Size

At the very least, Forktail Rainbowfish need a tank size of at least 20 gallons. This is suitable for a small group of fish.

Author Note: If you have the space, a 30-gallon tank is far better.

Some fish keepers make the mistake of thinking that these fish can be kept in tiny tanks because they’re so small. However, there’s a reason why a sizable aquarium is a must with Forktail Rainbowfish. 

These freshwater fish need plenty of swimming space. Not only that, but they are much happier and healthier when kept in groups.

Providing that extra room will allow you to keep a larger group together. Plus, it provides more open swimming space for the fish to enjoy!

Water Parameters

The best way to keep Forktail Rainbowfish happy and healthy is to replicate their natural habitat in the wild. Their native waters are slow-moving and surrounded by vegetation.

The streams they call home are usually surrounded by tall trees and plants. This has an effect on water quality. It’s best to mimic those conditions as closely as possible.

The good news is that the Forktail Blue Eye Rainbowfish isn’t very picky. It can adjust to many conditions. As long as you stick within the following acceptable parameter ranges, you should be fine.

  • Water temperature: 75°F to 79°F
  • pH level: Between 6.0 and 8.0 (around 7.6 is optimal)
  • Water hardness: 5 to 12 dKH

We recommend investing in a reliable thermometer to make sure your aquarium heater is accurate. Their water temperature window isn’t very large, so you want to get it right!

Setting Up The Inside Of Their Tank

The decor in your tank can help this fish thrive and make their vibrancy really pop! They do best in natural setups that mimic wild streams.

Start with a dark-colored substrate. Forktail Rainbowfish usually occupy the middle of the aquarium, but a dark substrate and backdrop can highlight their vivid coloration.

Next, add a variety of plants to the mix. These fish like feathered plants. Fine-leaf aquatic moss and floating plants with dense roots work well. You can try everything from Water Hycaninth to Java Moss.

Author Note: The plants act as a shelter for the fish. They also diffuse some light to make things more comfortable. You may also find your fish playing in the plants. They like to dart in and out of plants to have fun!

To complement the plants, incorporate some rock formations and driftwood. Just a few can make a bit difference.

Your filtration system should be efficient enough to cycle the tank frequently, and also help to oxygenate the water. Forktail Rainbowfish like some movement in the water, but it can’t be too strong.

Finally, there’s the lid. Make sure you get a strong and secure lid! These fish are known for jumping out of the water to their death (something not many owners are prepared for).

Common Possible Diseases

The good news is that Forktail Rainbowfish aren’t affected by any species-specific ailments. But, they can experience all of the standard freshwater diseases. This includes Ich, parasites, bacterial infections, and fungal infections.

Pseudomugil furcatus

The most common disease aquarists have to deal with is Ich. It’s a contagious disease that flares up when fish become stressed. Stress causes the immune system to weaken, allowing the disease to take hold.

The same can be said about most freshwater diseases. The best thing you can do is keep the tank in good shape to avoid unnecessary stress for your fish. This means frequent cleaning, routine water checks, and regular water changes.

All of these maintenance tasks will help you keep ammonia and nitrate levels under control. It can also help you spot potential changes in the water before they cause any problems.

Food & Diet

Forktail Rainbowfish aren’t picky when it comes to food. They’ll eat just about anything and have no special requirements.

You can provide standard nutritionally balanced dry flakes as the stable of their diet. To complement that, provide snacks of live or frozen foods. You can offer brine shrimp, cyclops, and daphnia.

Author Note: Only feed as much as the fish can eat in about two minutes. Avoid overfeeding to preserve the water conditions as well (too much extra food in the water can lead to serious problems).

Behavior & Temperament

These fish are very peaceful and playful. They get along just fine with most other peaceful species.

The only time you’re going to encounter aggressive behavior is around breeding time. Males will often put on a show and spar a bit. Don’t worry though, this behavior is innocent enough and usually doesn’t cause any injuries!

Forktail Blue Eye Rainbowfish may also have some problems with slow-moving fish that have long-flowing tails. They’re notorious fin-nippers, so it’s best to keep those types of fish out of the tank.

Forktail Rainbowfish are easygoing and will spend most of their day swimming around the tank in groups. They’re agile swimmers, so don’t be surprised if you see the fish darting from one end of the tank to the other!

Forktail Rainbowfish Tank Mates

As we mentioned earlier, these fish do best in groups. It’s important to keep at least six fish together. If you have a larger aquarium, aim for at least ten fish!

Staying in a group will help the fish feel safe and confident. Solitary Forktail Rainbowfish will spend most of their time in hiding. They may even lose their color.

To keep male-on-male aggression to a minimum, try to keep more females. There should be at least one female for every male. If possible, do two females to every male.

In addition to fish of the same species, Forktail Rainbowfish can cohabitate with other calm tank mates. They do fine with fish that occupy other parts of the water column.

Keep things peaceful and avoid any large fish that could eat the Forktail Rainbowfish for lunch!

Here are some good tank mates for the Forktail Rainbowfish:


Forktail Rainbowfish are quick to start breeding in captivity. Because of their shorter lifespans, most are ready to spawn when they’re about eight months old.

Breeding is a bit different for this species. To increase the chances of survival for the fry, create a separate tank for the eggs. Make sure to match the conditions of the breeding tank to avoid any shock issues.

These fish can breed in their primary tank, but you can create a separate breeding tank as well. Either way, make sure that there is a lot of dense vegetation. Utilize feathery plants or spawning mops. Arrange them around the edges of the tank.

Males will claim one of the plants in the corner while the females stay towards the center. Around sunrise, the males will put on a show for the females. Eventually, she’ll follow on of the males back to his plant and start breeding.

Author Note: Forktail Rainbowfish are continuous spawners. They lay small batches of eggs over several days or weeks. You need to keep an eye out for eggs and move them to a separate tank. The adults will try to eat the eggs if they get the chance.

As the female continues to lay batches of eggs, the individual eggs will get smaller and smaller until she’s done.

Eggs take a while to hatch. Depending on water conditions, they could incubate for up to 21 days! The good news is that fish fry are free-swimming immediately after emerging from the egg. You can move straight to baby brine shrimp or infusoria.

Feed them several times throughout the day. Also, change 20 percent of the water every week to keep the tank in good condition as the fry grow into adults.

Wrapping Up

As you can tell, Forktail Rainbowfish care is pretty darn easy. These fish are very low-maintenance which makes them a perfect fit for aquarists of any experience level.

Owning these gorgeous and hassle-free fish is something that all aquarists should experience at one point. It’s a combination that you don’t find with many other species!

If you have any other questions about the Forktail Blue Eye Rainbowfish we’re more than happy to help. Just get in touch with us through the website and we’ll answer them as well as we can.

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