Hi. I have bred and raised angels in the hard water from the Florida aquafer with no problems. But it can be a problem. It depends on where your angels come from. I know some angel breeders that breed them in the softest of water, there is wisdom to this, after all, fertilization is much more effective in soft water, and fungus does not grow on unfertilized eggs for days in soft water.
However, these "pampered" angels do poorly when moved from soft water to hard water unless a prolonged adjustment period is made. And then when they grow out and spawn the eggs will seldom do well in hard water.
Angels that are bred and raised in hard water will spawn in hard water with very little problem. I will concede that the hatch rates will be lower, but if you are going to breed angels that will be sold to retail shops you want a robust fish that is going to do well in retail water.
Pampered fish seldom do well when put into a retail environment.
You could always resort to using an RO water mixture to keep your fish and do water changes with. And if you breed them then you could grow out the subsequent fry in hard water to sell.
There are so many options. Bill