Which softness matters?

[siemanthepieman]

I had a quick search and could not find the answer but apologise if it has already been answered.

I have always wondered which 'softness' is the one referred to when you are told that Discus like soft water.

Is it gH or kH or both that should be low?

I have gH of 120ppm and kH of 40ppm.

I have read these are reasonable levels for Discus but I still think this gH level too high?

I would say kH is a bit low but my pH is very stable at 6.5, although this would obviously drop overnight in my planted tank.

Thanks in advance.

[ILLUSN]

those levels are fine for discus, i run a kh of 0 and a gh of 60-80 but i'm constantly changing water to avoid any buldup of organics and a ph crash, with your water you'll have alot less problems (my target ph is 4.5-5.0 hance i need to keep the kh at 0)