Adding fish to a cherry shrimp tank carries an asymmetry every keeper should respect: the fish can survive mistakes that would wipe out the colony. Shrimp react to traces of substances fish shrug off, they cannot be moved quickly when something goes wrong, and baby shrimp are on every small fish's menu. Quarantine, run with the shrimp as the protected party, is how you check a new fish's health — and its history — before it shares water with animals that fragile.
Why the shrimp set the standard
A fish arriving from a shop system may have been exposed to treatments used on neighbouring tanks, and residues clinging to the fish, its water, or a shared net can be enough to distress invertebrates. Shrimp also moult, and a moulting shrimp exposed to a sudden chemical or biological insult has almost no reserves. Meanwhile the fish itself may carry the usual shop-tank illnesses, which you would then be treating inside a tank full of animals that tolerate treatment worst. Every part of quarantine exists to keep those two problems out of the colony's water.
The quarantine tank, kept truly apart
Set up a separate small tank — bare bottom, heater if the species needs warmth, a cycled sponge filter, and a hiding tube — in a different spot from the shrimp tank, with its own net, bucket, and siphon stored beside it, not with the main kit. Acclimate the new fish into this tank gradually, throw their bag water away, and feed and observe them here for the whole period. Nothing from this tank, down to a wet hand, goes to the shrimp tank on the same round of chores.
Observing the fish, thinking about the shrimp
Watch daily for strong feeding, clear skin and fins, and settled behaviour, and think ahead to shrimp-specific questions while you watch: is this fish an active hunter that will spend its days stalking baby shrimp through the moss? Does it dig, uprooting the plants the colony shelters in? A healthy fish can still be the wrong fish, and quarantine is your chance to see hunting behaviour in a bare tank before the colony sees it too. Any illness signs mean the fish stays put and you seek an aquatic veterinarian's advice.
The treatment trap, handled honestly
If a quarantined fish does become ill, take great care: many common fish treatments are dangerous to shrimp, and a treated fish should not be transferred on the strength of looking better. Ask the veterinarian directly about shrimp safety and about how the fish and its equipment should be prepared before any move, and be prepared for the answer to be a much longer wait or a permanent separate home. Never treat the shrimp tank itself to solve a problem a fish brought in; prevention through quarantine is the whole strategy.
A careful final introduction
When the fish has stayed healthy, untreated, and well fed through a full observation period, blend it gradually toward the shrimp tank's water, net it across without any quarantine water, and release it where the colony has deep moss and plant cover to retreat into. Watch its interest in the shrimp over the following days; persistent stalking means the pairing fails and the fish comes out. Logging the fish's quarantine history in KinsLe Family Sharing ensures anyone tending the colony knows exactly what the new fish has — and has not — been exposed to.