A bottom fish found on the floor is a clue
Kribensis spend their lives near the substrate, hovering at cave mouths and picking through the lower layer of the tank. Jumping is not part of their normal behaviour, which is precisely why an escaped krib is worth investigating rather than just preventing. In almost every case something drove that fish upward with enough urgency that open air looked better than staying — usually a pursuer it could not shake. The lid you fit tonight stops the next escape from being fatal, but unless the pressure below changes, the same fish will keep hitting it.
Close the exit while you solve the cause
Start with the barrier anyway: a lid that sits properly, with the filter and cable openings covered, because a chased fish aims for corners and the back edge where equipment breaks the rim. Kribensis are strong for their size and can lift a light, loose cover at a corner, so check that yours stays seated. Lowering the waterline slightly adds a margin during the days while you work out what is driving the behaviour, and a dim evening check with a torch will show you where each fish is sleeping — a krib roosting near the surface, far from the caves, is a fish that has been evicted from the bottom.
Give a chased fish somewhere better to go
The real fix is architecture. Kribensis need caves — flowerpots, coconut shells, rockwork with genuine enclosed hollows — and they need more caves than fish, arranged so sightlines break between them. A subordinate that can vanish into a cave on the far side of a plant thicket stops being chased; one fleeing across open sand has only the vertical left. Rearranging territories when you add or separate fish also helps, since moving the landmarks resets who owns what and gives an underdog a fair claim on a new shelter.
Breeding changes everything
A peaceful pair can turn the tank upside down when they spawn. Parents guarding eggs or fry will drive every fish from their corner, and a former mate can become the target if a bond breaks down. During breeding, watch whether one fish is being relentlessly pursued, hovering at the surface, or showing frayed fins — those are signs to separate the victim into another tank rather than relying on the lid. Overcrowding juveniles from earlier spawns creates the same pressure, so move youngsters on before the tank's cave real estate runs out.
Water and routine checks
Test the water whenever a bottom fish behaves out of character, because deteriorating conditions make kribensis restless and irritable, and irritability in a territorial cichlid becomes somebody else's emergency. Keep feeding varied and delivered low in the tank so competition at the surface never develops, and do water changes gently — a siphon chasing fish around bare glass can trigger the very flight you are preventing. Stability, cover, and space solve this problem together; the lid is simply insurance while they take effect.
To catch the early signs, KinsLe's Care Teams lets you assign care duties per kribensis tank — water tests, cave checks, and watching the pair — with completed tasks marked by a timestamp so nothing is assumed done.