This article below may help.
The main thing too, with treatment is to make sure the water parameters are excellent. Maybe the water the fish is in is new water treated with water conditioner from the tap. If it was water taken from the tank it is in, you would want to do some water changes to get it in better condition to start.
Temperature matched and treated with water conditioner which treats chlorine and chloramine.
As in summer many water treatment facilities use chloramine because it is stronger and being stronger will also require additional drops of some dechlorinator, and some brands do not treat it, so can harm your fish and beneficial bacteria.
https://www.aquariumadvice.com/fish-...and-treatment/
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New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish?

Start here - Aquarium Advice Article
https://www.aquariumadvice.com/guide...ater-aquarium/
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