Coral substrate

[RovingGinger]

I’m struggling to find comprehensive information on how to use ground coral in or as substrate. I ended up with a small bucket full along with two free tanks, along with some white coral pieces. 
 

I have 3 bumblebee gobies who I’d like to move to a 12 gallon nano. They are in fresh well water, very hard and high Ph. Is this a good use case? Or since I already have high ph, is it not for me? 

[Bill Smith]

In my experience, crushed coral is a perfectly serviceable substrate for freshwater tanks. Even though I also live in a place with hard water and high pH, my multi colony loves it:

I don't think there is any harm in using as a full or partial substrate in a tank where your fish are suited to hard water and high pH, even if your water already has that. I don't really think it will make the water any harder or raise the pH to any noticeable degree, if they're already high. I think it will serve to increase your buffering capability.

But for folks who want to use crushed coral for soft/acidic tanks, I've heard 1 pound per ten gallons as a common measure to help raise and buffer the pH and hardness.