Why the vacuum catches animals at all
A gravel vacuum works by drawing a column of water and loose debris up the bell, and anything small and light in that column rides along. Baby cherry shrimp are the classic passengers — nearly transparent, weaker swimmers than the current, and fond of grazing exactly where debris collects — but fry, tiny snails you wanted to keep, and even a curious small fish investigating the tube can get pulled toward the intake. The suction is strongest at the bell's mouth and falls off quickly with distance, which is the physics you exploit: keep the mouth where the dirt is and the animals are not, and modulate the flow so anything that drifts close can still swim free.
Throttling the flow with a pinched hose
Your throttle is the flexible hose. Pinch it partway closed, or kink it gently, and the siphon's pull drops instantly — practise on plain water first so the pinch becomes reflex when a shrimplet wanders into range. With the flow throttled, hover the bell a finger's width above the gravel: settled mulm lifts into the gentle current while the gravel itself, and anything with fins or legs, stays down. For a deeper clean in an animal-free patch, push the bell into the gravel, let the stones tumble and release their dirt, then pinch the hose as you lift so the gravel falls back instead of following the water up. Work slowly; a gravel bed cleaned in calm sections beats a tank stirred into soup.
Working around plants, moss and hiding places
Divide the tank into zones and treat them differently. Open gravel gets the full plunge-and-lift treatment. Planted corners, moss clumps and the undersides of wood are nurseries — shrimplets and fry shelter there precisely because the current cannot reach — so skim the bell over their surface at most, or skip them for this session and cover them lightly next time. Shoo fish ahead of you with the bell's slow approach rather than chasing debris into their hiding spots, and keep one eye on the far end of the tank: the fish you are not watching are the ones investigating the tube. Bright light helps — vacuum with the tank light on and your reading glasses if you need them, because a half-centimetre shrimplet is easy to miss in shadow.
The bucket check, and sharing the duty
Before the bucket goes to the sink, hold it against the light and wait a moment. Shrimplets and fry that rode the flow settle, then start swimming in small, unmistakable jerks; a fine net or a cup scoops them back into the tank unharmed, and after a few sessions you will recognise the bucket-check as simply part of the job. The water itself can still be discarded once its passengers are home. Gravel vacuuming is the tank chore people most often postpone, because it feels fiddly — sharing it helps. On KinsLe, the vacuum round can rotate through Care Teams with the pinch-and-hover notes attached, so whoever's turn it is works the gentle way and the shrimplets stay where they belong.