Scissortail Dartfish (Ptereleotris evides)

The Scissortail Dartfish (Ptereleotris evides), also sold as the Scissortail Goby or Blackfin Dartfish, is a slender, peaceful plankton picker that hovers in open water above the rockwork and flicks a deeply forked, black-edged tail. It is an easy, reef safe fish for a covered tank, but it is nervous: it hides for its first days in a new home and it will jump from any open gap when startled. Browse the rest of our saltwater fish and supplies.

Lid First, Then Everything Else

Dartfish lose more often to the floor than to disease. When something startles them (a hand in the tank, a net, the lights snapping on, a bully) they shoot straight up, and a gap the width of a finger is enough. Cover the whole top with a tight lid or mesh screen, including the cut-outs around cords, heaters and the overflow, before this fish goes in. Fade the lights on and off where you can, and keep the tank free of fish that chase.

Care Guide

• Tank size: starts in a 30 gallon with open swimming room above the rockwork. Plan on 55 gallons or more as it grows toward 4 to 5 inches, or if you want to try more than one.
• Lid: required. A tight lid or mesh screen over every gap, every time.
• Water: 72 to 78°F, salinity 1.020 to 1.025, pH 8.1 to 8.4, moderate flow. Stable, mature saltwater.
• Diet: a carnivore that picks food out of the water column. Offer small meaty foods two or three times a day: mysis, enriched brine shrimp and small pellets. A slim fish like this one shows hunger fast, so small frequent meals beat one big one.
• Temperament: peaceful toward other species, but it can quarrel with its own kind. One per tank is the safe plan.
• Shelter: give it a cave or hole low in the rockwork and some sand or rubble. It hovers near its bolt hole and dives into it when worried.
• Watch for: a dartfish that is bullied stops coming out to eat and slowly starves. Check that it is actually getting food at every feeding during the first weeks.

Specifications

Compatibility

The Scissortail Dartfish does best with calm community fish that will not chase it or outcompete it at feeding time: Ocellaris Clownfish, Green Chromis, Pajama Cardinalfish and small gobies such as the Yellow Clown Goby are good company. It ignores corals, clams and the cleanup crew.

What goes wrong: dottybacks, aggressive damsels, hawkfish and larger wrasses bully it until it hides and stops eating, and lionfish, groupers and triggers will eat it. Two dartfish, or a dartfish and a close relative like the Zebra Bar Goby, can fight as adults unless the tank is large. It is also not a shrimp goby. It does not share a burrow with a pistol shrimp, so do not buy it for that job; shrimp gobies such as the HiFin Banded Goby are the ones that partner with pistol shrimp.

Recommended Foods & Supplies

• Piscine Energetics PE Mysis or Hikari Bio-Pure Frozen Mysis Shrimp as the daily staple
• SFBB Mysis Shrimp Cube for variety
• Ocean Nutrition Formula 1 Pellets in the small size for a dry food it learns to take mid-water
• Selcon to soak frozen food a few times a week

FAQ

Why is my dartfish hiding all the time?
That is normal for the first several days to a couple of weeks. It hovers near its cave and darts in at every movement until it trusts the tank. Peaceful tank mates, a cave of its own and dim lights at feeding time bring it out sooner. If it still hides after a few weeks, look for a fish that is chasing it.

Will it really jump?
Yes. Jumping is the number one way these fish are lost. Cover every gap before it goes in, including the back strip around cords and plumbing.

Can I keep more than one?
One per tank is the safe plan, and this listing is for one fish. Juveniles sometimes get along, but adults can turn on each other. If you want to try a group, use 55 gallons or more, add them on the same day, and have a backup tank ready.

Is it reef safe?
Yes. It eats plankton and small meaty foods and leaves corals, clams, snails, crabs and shrimp alone.

Will it live with my pistol shrimp?
Not as partners. Dartfish do not team up with pistol shrimp the way shrimp gobies do, and a big pistol shrimp can even be a threat to a fish that sleeps in the rockwork. If a pistol shrimp partnership is the goal, choose a shrimp goby instead.

What tank size do I really need?
A 30 gallon with a tight lid is a fine start. It grows to 4 or 5 inches and spends its day swimming, so plan on 55 gallons or more for the long run.