Ram fry in alkaline water

You will have a very hard time getting the eggs to be fertilized in that water. Having water like that hardens the eggs so the sperm from the male can't penetrate them. Its possible you could get a few fertilized eggs, but nothing much if at all. Growing the fry out in that water on the other hand would be no problem. Having the higher amount of minerals in the water actually encourages faster growth. Its very similar to growing out discus, in hard alkaline water with a high amount of TDS the discus fry will have better finage, and grow faster than their counterparts in soft acidic water, and have a far superior shape. Just getting fertilized eggs in that water is next to impossible.

Since it's only a 20g, you might try cutting the tap water with RO water (or distilled water) over the next several water changes. That should get the gh down. Look for another spawning attempt in anywhere from 2 to 4 weeks. Although buying distilled water or RO water could get expensive after awhile, and there's no gaurantee the next spawn will be succesful. Rams have a reputaion for needing several spawnings in order to get it right. This is often attributed to the practice of artificially hatching and rearing rams (the babies don't get to see what good parenting is all about). You see it in alot of cichlids, but rams are notorious for it.

Talk to EMG. She has similar PH and her rams won't stop mating. I've got a pair from her, and they're doing great.

PH has nothing to do with if the rams will spawn or not. They will in alakline or acidic water no problems. The problem comes when trying to get fertilized eggs, Rams are bad parents to begin with, even parent raised ones may need to be a year to a year and a half old before they will start getting the hang on things. Till they reach that age I wouldn't really do much with your water, just let them practice on the non fertilized eggs, and then when they fully mature, start getting your TDS (Total dissolved solids, what makes the water hard) down. I would do this gradually, start adding only 10% RO water for the first week, 20% the second and so on just to be on the safe side.