my kh is 240 and my gh is 140 and my fish have no problems with it at all. what kind of fish do you have or want to put in there?
i have von rio tetras, otos,bristlenose plco,clown loaches,apple snails,ramshorn snails,scizortail rasboras,panda cories,peppered cories,black neons,glowlights,albino plco,false siamese algae eaters,chinese algae eaters,tiger barbs(norm and green).
and all these fish have no problem with the hard water.
my PH is also high at 8.5