If you have a Pokemon that can learn Waterfall (apart from Golduck) then No.
If you have no other Pokemon, then delete Scald for Waterfall.
I'll tell you its decent ingame, but looking at Golduck's stats and the moves you taught him, I wouldn't. It depends on what stat your Golduck's better in.
Attack: Go with Waterfall and delete Scald
Special Attack: Don't teach it Waterfall.
My ingame Experience: Yes.