Blue Eyed Beauties

There is a small, peaceful hardy aquarium fish that is popular among home aquarists. They are stunningly colored and active with very interesting behaviors, especially as it relates to dominance and breeding displays. Even more interesting, this small fish is really only ever available as an aquacultured specimen. They have a tiny wild range, and the only place they've ever been found is in a few rivers of eastern Papua New Guinea. It is widely thought that all of the fish available to aquarists around the world are all the descendants of fish gathered in a single collection in 1981. This has been a hard claim to prove or refute, so we present it here and you can make up your own mind or do your own research about its veracity.

Some of you will have guessed the fish by this information all ready, but for the rest of you, we're talking about Pseudomugil furcata. They have a few different common names, but are usually known as Forktail Rainbowfish, at least here in North America. You may also see them at your favorite fishy retailer labeled as Blue Eyed Forktails, Blue Eyed Rainbowfish, or less frequently Furcata (or Furcatus) Rainbows.

These fish are stunningly colored, and when mature, they are a pale translucent yellow, with absolutely brilliant yellow tips on all their fins and deeply forked tails that give them the “furcatus” part of their name. They don't get very big, and the largest wild specimens every collected and documented were less than two inches long, though over the years a few home aquarists have reported theirs getting a tad longer at about two and three quarters inches. Even though they are very small, they are also incredibly active, and do best kept groups, so they need a slightly bigger aquarium that you might think. A 20 gallon (long format tank) could house a group of ten throughout their lives. They are also a very peaceful fish and can be kept with a wide range of other fish and so your tank size might be dependent on the other fish you intend to keep. Whatever the size, be sure to cover the tank, as these fish live in the upper level of the aquarium and do a surprising amount of jumping when startled.

After being aquacultured for over 40 years, their wild habitat is technically of little bearing when planning a display for them. That being said, their wild home rivers are clear and clean and feature dense vegetation, and this is both an excellent looking display and physically appropriate for keeping them. Lushly planted aquariums will help Forktail Rainbowfish show off their best colors and make for the most interesting displays as males show off for the females in the group. Displays can also feature driftwood and smooth rocks.

In the wild Pseudomugil furcata is often found co-habituating with Peacock Gobies (Tateurndina ocellicauda) and these fish together make for a very interesting and biotope specific display. The needs of both fish are similar, though the Goby will do best with a nice soft, dark colored substrate, and the Forktail would be just fine without one. Other good tankmates would be any number of small Tetras like Cardinals or Neons; small Rasboras like Galaxies are another great choice. Corydoras work very well and bring a lot of activity and different looks to the lower levels of the water column. Some new aquarists make the mistake of buying only male fish for their brighter colors, but this isn't what you should do as they display best when there are females in the group. We suggest having at least nine, of which three or four should be male.

Forktail Rainbows are easy to feed, they were always so, and decades of captive breeding has just enhanced this. The only challenge (if one can call it a challenge) is that they are small fish, with small mouths. They're going to need an appropriately sized food. Think things like Gamma Rotifers, Cyclops, Copepods, and all Gamma's assorted enhanced Brine Shrimp products. A high-quality flake food is also an appropriate part of their diet as they like to eat near the surface or from it. They'll also happily take small live foods like microworms, daphnia and artemia nauplii.

These fish will do best in a very clean and biologically established tank. Pseudomugil furcata doesn't need or want a ton of flow (and neither will the plants) so balance filtration sizing with this in mind. Look for a filter that turns the tank over no more than five times an hour or so (ex. If you have a 20-gallon tank, the filter can be about 100 gallons per hour.) Keep up water changes to make sure the water stays very clean, and the nutrients stay in check; nitrates should be less than 20ppm at all times. Hardness will be mostly irrelevant, and pH should be fairly neutral to slightly basic, in the range of 7.0-8.0. They like warm water, so the tank should live somewhere in the 75–82-degree range. Warmer temperatures will increase the likelihood of your Forktail Rainbows spawning in your display.

If you're interested in spawning these fish, the process isn't all that demanding. In a well-established, and densely planted tank, you may even just see baby fish without any external effort. The success rate of this will not be good as Forktails are not good parents except in the most basic biological sense. Fine leaf plants and mosses or spawning mops that hide the eggs and small fry are a great way to increase success rates. Ideally these would be placed high in the water column to ensure that more of the eggs actually make it into them. Conversely you could use a fine net over the bottom of a breeding tank to keep the parents from consuming the eggs. Fry will hatch after about three weeks, and they can eat small foods like microworms and powdered flake or pellets.

Like many small, very active fish, Pseudomugil furcata is not a long-lived species. They grow quickly and can reproduce at an early age, but generally won't live more than a couple years, and their reproduction rates drop off pretty dramatically when they are a year and a half old. This is no reason not to get them, as a healthy group of them, with enough cover could likely breed enough to replace old specimens as they age out. These are amazing fish that are dazzlingly colorful and superbly active and interesting. If you're looking for another (or maybe just a different) schooling species to add to your peaceful community display, then think about Forktail Rainbows from Aquatropic as an option.