Congo tetras are the glamour fish of the African river tank — three inches of iridescent scale and trailing fin — and that size is precisely the problem for shrimp. A cardinal's mouth makes adult shrimp safe by simple geometry; a Congo's mouth makes no such promise. A healthy adult cherry shrimp is a mouthful this athletic schooler is entirely capable of taking, especially in the soft, helpless hours just after a shrimp has moulted, and a colony in a Congo tank typically dwindles to the few individuals too wary to leave the rocks.
What can genuinely share with Congos
Snails are the safe half of the question. Nerite and mystery snails are far beyond anything a Congo tetra attempts — the fish may investigate a snail once, discover shell, and lose interest permanently. Large amano shrimp occupy a middle ground: their size deters casual attacks and many keepers hold them with Congos for years, though even amanos lose their young and live nearer the cover than they would in a fishless tank. Small ornamental shrimp — cherries and their colourful relatives — belong in a different aquarium, full stop. If a breeding shrimp colony is a goal, build it around small-mouthed fish and let the Congos reign in a tank of their own scale.
Room and numbers shape their manners
Congos are river fish built for current and distance; a long tank with open swimming water is not luxury but temperament management. In a cramped footprint or a group of two or three, these schoolers turn insecure, and insecure Congos nip fins, chase tankmates and test everything edible-looking — including shrimp they might have ignored when settled. Six or more, with females in the mix, spreads their attention across the school and produces the calm, stately cruising they are prized for. Their jumping is real, too; a tight lid protects both the fish and the room. Give shrimplets no thought here — there will effectively be none — and instead enjoy the Congos with robust plants, sturdy tankmates and the big snails they ignore. Timing deepens the risk rather than softening it. Shrimp moult most often at night and spend their first soft hours hiding; Congos rest at night too, but a school startled by a light or a shadow will flare through the tank at speed, and anything soft-bodied in the open is fair game in that moment. Cover that protects shrimp from cardinals does not protect them here, because a hunting Congo works the planting methodically rather than snapping at what crosses the open water.
If the shrimp matter more
There is no planting thick enough and no feeding schedule generous enough to make a determined school of Congo tetras safe for a cherry colony; well-fed predators still hunt, because hunting is behaviour, not hunger. Choose which creature the tank is for and stock honestly around that choice. Many keepers run both pleasures in parallel — Congos commanding the big display, a modest shrimp-only or ember-tetra tank doing the delicate work beside it. Whichever way you split it, keeping each tank's true stocking written down in KinsLe's Family Sharing prevents the classic accident: a bag of new shrimp, bought as a surprise, released into the wrong water by someone who did not know what lives there.