When I switched to RC from IO, I started having fewer alkalinity problems. I haven't read anywhere that RC has lower alkalinity... posted results on other forums from actual users showed higher alkalinity levels than IO.
How much RC are you adding per gallon of water to make your sw? I started using a 1/2 c per gallon of water, did some testing, and found to get the specific gravity I want (1.025 - 1.026 on a refractometer) I need to add an extra 1/4 c to every 4 g of water. I make my water in empty salt buckets, so I make batches of water in multiples of 4 g. Adding enough RC to get that specific gravity, I end up with an alkalinity > 8 dKH and a calcium level of just over 400 ppm. By all means, double check these amounts yourself, verify you're getting the specific gravity you desire, and base how much RC you add on your individual results.
I do find myself adding calcium and alkalinity buffer between water changes to keep up with demand. But, it's not as often as when I was using IO. For that reason, I've decided to stick with RC. There's a lot of coralline algae in our tank, our snails show considerable growth on their shells, and our corals are growing at noticeable rates. I would say that I'm better off since I started using RC.
