Sixstrap grubfish

Where they come from

Sixstrap grubfish (Parapercis sexlorata) are little sand-perching predators from the Indo-Pacific. You will usually find their relatives sitting on open sand next to rubble and low rock, watching everything like a tiny hawk. That natural "perch and pounce" thing drives basically every care decision in the tank.

Setting up their tank

Think sand, space, and stability. This is not a fish I would toss into a fresh build or a tank that still swings in salinity and nutrients. They do best once your system has settled in and you have a routine.

• Tank size: I would start at 40-55 gallons for one. Bigger is easier if you want other sand sitters or active fish.
• Sand bed: fine sand, around 1-2 inches. They like to rest on it and may make little divots.
• Rockwork: keep some open sand in front. Build a few low ledges and rubble zones so they can perch and retreat.
• Flow: moderate. Let food settle a bit so they can hunt without it blasting past their face.
• Lid: cover the tank. These guys can jump if spooked, especially early on.
• Lighting: whatever suits your reef or FOWLR. They do not need special lighting, but give them shaded spots.

If you run a reef, they are usually fine with corals. The real question is whether your cleanup crew and small ornamental crustaceans are fine with them (more on that below).

What to feed them

They are meaty-food fish. Mine settled in fastest once I treated it like a picky predator and fed smaller portions more often at first. New arrivals can ignore flakes and pellets for a while even if they look "fine" otherwise.

• Great staples: frozen mysis, chopped shrimp, chopped clam, enriched brine (as a helper food, not the main diet), small pieces of squid.
• Best "gets them started" foods: live blackworms (if you can source safely), live ghost shrimp, live enriched brine, or freshly hatched/older brine for smaller individuals.
• Pellets: some will convert to sinking carnivore pellets, but do not count on it day one. Mix pellets into thawed food and let them associate the smell.

Feeding rhythm that has worked for me: for the first couple weeks, small feeds once or twice a day. After they are settled and holding weight, you can usually go to 4-5 meaty feedings per week depending on tank temp, tankmates, and body condition. You want a gently rounded belly after meals, not a constantly pinched look.

How they behave and who they get along with

Personality-wise, they are bold in a quiet way. They sit, watch, scoot, pounce. They are not usually open-water bullies, but they are absolutely predators, and anything that fits will get tested.

• Good tankmates: medium peaceful reef fish (tangs, rabbitfish, most wrasses that are not hyper-aggressive), gobies that are not tiny, blennies that can hold their ground, cardinals, chromis (adult size).
• Use caution: other sand perchers, hawkfish, dottybacks, aggressive damsels, big territorial clownfish pairs. They can get bullied off food or spend all day hiding.
• Not compatible: very small fish (tiny gobies), decorative shrimp you care about (sexy shrimp, anemone shrimp, small peppermint), small crabs. Snails usually fare better, but hungry fish make questionable decisions.

They like having a "home" spot on the sand with a nearby crevice. If you notice them pacing the glass or constantly relocating, the tank can be too bare, too bright, or they may be getting pushed around by a more dominant fish.

Breeding tips

Breeding Parapercis in home aquariums is not common. They are not like clownfish where you can predict the whole routine. If you keep a bonded pair and hit the right social setup, you might see courtship hovering and short dashes off the bottom, usually around dusk.

Common problems to watch for

Most issues I have seen with sand-perching predators come down to shipping stress, not eating, and getting outcompeted at mealtime. If you get past the first month and they are eating well, things usually get a lot smoother.

• Refusing food: common in new arrivals. Try smaller meaty items, feed with a baster, dim the lights, and keep boisterous tankmates away during feeding.
• Skin/fin damage from rough substrate: shows up as frayed fins, raw spots on the belly, or redness. Swap to fine sand and keep water clean while it heals.
• Parasites (ich/velvet): they can look "dusty" or breathe fast while still perching. Quarantine is your friend with advanced fish like this.
• Bacterial infections after shipping: cloudy eyes, redness at fin bases, sores. Often tied to stress and minor injuries.
• Jumping: usually early on, after chasing, or during sudden light changes. A lid fixes most of it.

One last practical thing: take photos every week or two. With perch-and-pounce fish, slow weight loss can sneak up on you because they do not "act" sick until they really are. A quick side photo under the same lighting makes it obvious if the belly is getting hollow.