Alan Silver wrote:

I haven't done anything with him yet. The thought of trying to get him
out of the water is a little daunting !! He's a perky fellow !!

Assuming I can catch him, what concentration of salt, and for how long ?
Also, do I need to worry about the hardness and pH of the water for the
(presumably) short duration of the dip ? Our water is soft and neutral
out of the tap, whereas the tank water is hard and alkaline.


Use the tank water....in a tub or CLEAN bucket....if its a parasite just
get some tweezers and gently pull it off.
Salt dip solution....you could try 10 tablespoons per gallon for about 3%
solution
and just dip for as long as your fish is not stressed too much (he will stress a
bit)
Others here may have different suggestions.