Is crushed coral good for keeping Ph from crashing?

[RTR]

Nitrification has a huge effect on KH and in turn on pH. For every milliequivalent of nitrogen oxidixed from ammonia to nitrate, two milliequivalents of bicarbonate are used used up. If nitrate being developed in your tank? If you have any living critters, it is. If so, you are using KH up at twice that rate.

 

[Slappy*McFish]

So, yes....
Use the crushed coral. It will help keep the KH and pH stable.