Thanks Caryl.
I ending up buying a KH tester and KH up as the girl at HFF convinced me it was needed (no kh level showing). But the guy at the other shop reckons you dont need to worry about KH with the type of fish I have. (Platties, pleco, kribs, gourami). And he still insists I need new gravel.
I have been sucking thru the gravel when I change the water once a week - could I be doing that to often?
I dont think its my pleco - he is still quite young only about 7cm long I would say.