Someone selling cichlids told me me it just takes a piece of coral in the water to harden the water. Is this true?

Coral can raise pH and harden water, yes.

Limestone is ancient coral, it also raises pH and buffers water.

I'd personally just find a fish store that sells Texas Holey Rock, that way you give the fish holes that they like to hide in.

Somewhere on the internet I converted 150 ppm (my water) to be 8.4 dhk? Would you go by this chart?



0 - 4 dH, 0 - 70 ppm : very soft
4 - 8 dH, 70 - 140 ppm : soft

8 - 12 dH, 140 - 210 ppm : medium hard

12 - 18 dH, 210 - 320 ppm : fairly hard
18 - 30 dH, 320 - 530 ppm : hard




I'm finding that on different websites, the water hardness scales vary?