One important thing to remember is that hard water will cause the shells of the eggs to harden, and in very hard water the shells can become too hard and make hatching difficult or impossible. If the water is too soft, the eggs may instead collapse. The water in my area is generally ROCK hard in gh and kh. PH is also at the top end at 7.8 to 8.0. The fish adjust to these numbers well enough but hatching can be affected greatly. You can mess with the water here to lower with rain or bottle water, peat mix but you have to be careful as sudden changes can be fatal. For now Im making ial tea and pre adjusting some water in a tub making a more perfect water just for a spawn.
Proud IBC member