The eel-like fish that vanishes for a living
Kuhli loaches are slender, banded, eel-shaped loaches from Southeast Asian forest streams, and their defining behaviour is disappearance: by day a healthy kuhli is wedged under wood or buried in substrate with just its head out. A first tank of 20 gallons long suits a group, and the layout should embrace the hiding rather than fight it - the more secure cover a kuhli has, the more it will actually show itself at dusk. Judge success by evening activity, not midday visibility, and do not panic-buy a replacement for a fish that is simply under the driftwood doing its job.
Sand they can dive into
Substrate decides whether kuhlis thrive or merely survive. They burrow nose-first when startled and forage by sifting, so cover the floor with soft sand or the finest, smoothest rounded gravel; sharp or coarse gravel scrapes their scaleless skin and invites infection. Layer the tank with hiding architecture: driftwood tangles, stacked smooth stones with gaps between them, coconut caves, and a scattering of dried leaves, which kuhlis drape themselves through like hammocks. Plants root fine in sand with root tabs and add the shade these fish prefer. Keep light subdued or floating plants overhead, and the loaches will be out far more than the books suggest.
A lid with genuinely no gaps
Kuhlis are the escapologists of the small-fish world. They explore filter intakes, climb into hang-on filters, and leave through gaps around pipework that look far too small for a fish - and then they are found on the floor in the morning. Fit a tight lid, block cut-outs with foam or mesh, guard the filter intake with sponge, and check any external filter for a loach living comfortably inside it before assuming one has died. Warm, soft, gentle water around 75 to 82 degrees suits them, with stable chemistry prized over exact numbers, and the tank must be cycled before they arrive, since scaleless fish suffer first and worst in ammonia.
Six or more, fed after dark
A single kuhli is a permanently hidden kuhli. In groups of six or more they gain the confidence to forage in the open at dusk, pile companionably into the same cave, and show the looping, noodling behaviour that makes keepers love them. Feeding must be deliberate: they are nocturnal scavengers, but scavenging is not a diet, so drop sinking pellets, small wafers or frozen bloodworm in after lights-out, near their cover, where daytime tankmates cannot clear it first. A kuhli in good condition is plump behind the head; a pinched, skinny one in a community tank is being outcompeted, not ill.
Tankmates and the long term
Kuhlis are defenceless and entirely peaceful, so their tankmates must be too: small rasboras, tetras, corydoras and gouramis all share well, while anything that hunts the bottom at night or nips at resting fish does not. They are also long-lived for a small fish - well past ten years is achievable - and notably hardy once the tank is mature and the escape routes are sealed. Most kuhli losses happen in the first month, in new tanks, through gaps in lids, which is why this setup spends so much attention on sand, cover and sealing rather than on water fine-tuning.
Shy nocturnal fish are exactly where holiday care goes wrong, because a sitter feeding at noon sees nothing and assumes the fish are gone or need nothing: KinsLe's Care Pass gives your sitter the kuhlis' real routine - what to drop in, where, and after lights-out - as temporary, clear access while you are away.