Rescue fish from a closing tank arrive with generosity on one side and uncertainty on the other. The keeper is rehoming them because the tank is ending, not because the fish were chosen for your water, your stock, or your experience. Preparation is what turns a kind offer into a successful adoption, and most of it happens before any fish is bagged.
Build the quarantine tank first, and cycle it properly
Set up a separate quarantine tank with a mature filter, a lid, subdued light, and cover in the form of plants or shelters, because new arrivals that can hide feed sooner and stress less. If the species need heated water, fit a heater and verify the temperature holds steady for several days. The filter must be genuinely cycled, either mature media from an established tank or a cycle completed in advance, and you should confirm that with tests showing no ammonia and no nitrite before collection day is agreed.
Keep quarantine equipment separate from your main tank's nets and siphons, or clean shared items thoroughly between uses. The whole point of quarantine is a barrier, and a shared net quietly demolishes it. Match the quarantine water's temperature and general chemistry to what the fish are coming from where you can, because you can adjust conditions gradually during quarantine far more safely than on arrival day.
Question the keeper while the tank still exists
Ask the keeper for the full list: every species, how many of each, how long they have had them, and the adult size each fish will reach. Ask about recent deaths, any treatments used in the tank and when, what the fish are fed and how eagerly they eat, and the tank's recent water readings if the keeper tests. Ask why the tank is closing, without suspicion, because a keeper moving house and a keeper who has been fighting persistent problems are handing you very different risks, and you deserve to know which.
Decide from those answers which fish you can genuinely take. A rescue into the wrong home helps nobody, so decline fish whose adult size, water needs, or temperament do not suit your tanks, and say so early enough for the keeper to find them another home. Taking every fish out of kindness and overstocking your quarantine tank converts one closing tank into two problem tanks.
Plan the move and the arrival
Take strong fish bags, elastic bands, and a dark, insulated box to the collection, and bag the fish at the keeper's tank with plenty of air above the water. Keep the journey direct and the box level and shaded, because bagged fish have no temperature control and limited oxygen. Float the closed bags in the quarantine tank to equalise temperature, then open them and add small amounts of quarantine water gradually before releasing the fish, and never tip the bag water into your tank.
Feed lightly on the first day, and only once the fish are exploring rather than hiding motionless. Dim light and a quiet room for the first evening do more for new arrivals than any additive.
Observe for four weeks before any promotion
Keep the fish in quarantine for four weeks, watching feeding, breathing, fins, skin, and behaviour daily, and testing the water regularly because a newly stocked filter can falter under a sudden load. Note anything you see with dates, because a dated note distinguishes a fish that arrived thin from one that is losing weight with you. If a fish shows signs that concern you, seek advice from an aquatic vet or an experienced fish health source promptly rather than treating the whole tank on a guess.
Only after four weeks of clean observation should fish move to a main tank, introduced in a way that respects the existing stock's territories. KinsLe's Transferrable Profiles lets the closing-down keeper transfer each fish's feeding and history notes to you with its profile, so the knowledge held in the old tank survives its closure.