A leak or an urgent repair leaves no time for a full teardown, so protect the fish first and the furniture second. Decide where the tank is going before you touch it, clear that surface, and gather a board, towels, a lidded container and a bucket for tank water. Switch off the electrics at the wall, then unplug the heater and filter so nothing runs dry or overheats as the level falls.
Decide Whether He Stays in the Tank
For a short slide across one room, a small tank can travel with the betta still inside once much of the water has been drawn off into the bucket. Slide the whole tank onto the board instead of gripping its rim, keep it level, and have two people carry the board so the glass never twists. If the tank is large, the route involves stairs, or the repair will take hours, net him gently into the lidded container filled with his own tank water instead. Put the lid on, wrap the container in a towel to hold warmth and darkness, and set it somewhere quiet and out of the way of the work.
Protect the Water and the Filter
Save as much of the original tank water as your bucket allows, because refilling with familiar water spares him a sudden chemistry swing on his return. Keep the filter media submerged in that saved water the whole time: the bacteria living on it are what process his waste, and media left to dry out, or rinsed under a chlorinated tap, loses much of that colony. Keep plants and decor damp in the same way, and work promptly throughout — a betta waiting in a small container has no filtration, so the clock matters more than tidiness.
Set the Tank Back Up and Watch Him
Once the tank stands in its new or repaired spot, refill it with the saved water first and top up with conditioned water matched to the usual temperature. Restart the filter and heater, check that both are running, and test the basic parameters before he goes back. If he travelled in the container, rest it in the refilled tank so temperatures equalise, then tip him in gently. Keep the lights low for the rest of the day, offer a small feed once he is exploring again, and watch him over the next couple of days for clamped fins, hiding or refused meals — the signs that the upheaval, rather than the new position, is still bothering him.
Be Ready Before the Next Emergency
A calm rehearsal is impossible with a leak already spreading, so store the board, container and bucket near the tank rather than in a distant cupboard, and keep his profile details and a recent clear photo current while nothing is wrong. Should a pet ever go missing from home, his KinsLe profile carries the Lost Pet Alert System at no cost; the alert appears on a map, and whoever finds him can send you a message through it.