Okay that's fine, the clean warm water should really help him out! He may be old but I don't think he's done yet lol.
When you add the new water in, make sure to condition first and if you can, don't just pour it in but gradually add it in over half an hour or so. I know it's a longer amount of time, but you don't want to stress him out too much, you know? So he definitely just needs some special care