As momar suggested, crushed coral is a good way to add some calcium. IME with 40ppm out of the tap, it added another 20ppm to the tank water. It's rather limited on how much it will put in. Yes, it will raise the pH, but I wouldn't worry about that. Fish don't read pH (to quote RTR and Daveedkareptileguy2727 said:bigger tank simply equates to better growth and health overall (which can be ruined if you dont keep up with the maintenance). my 3 goldfish are in a 55. they are doing very well on the diet they have, as well as the water change schedule of 50% weekly. what would be the best supplements than to increase the hardness for them? epsom salt adds magnesium right? what would be the best way to add calcium?

You can also buy Seachem's Equallibrium, which is a GH booster, or Tom Barr's GH Booster (much cheaper and just as good if not better).
I use 1 tsp of Barr's Booster after every water change in my 75gs, but then I also dose MgSO4 (magnesium) and a mix of CaCl2 (calcium chloride) and CaCO3 (calcium carbonate) every second day between water changes. Those tanks are heavily planted, btw, and no goldfish.
My levels in my planted tanks are usually around Mg 10-26ppm and Ca 100-150ppm, GH runs 20-25 dGH. Levels in those tanks depend on how many red stem plants I have.
You can get Tom's GH Booster from Gregg Watson here: http://www.gregwatson.com/proddetail.asp?prod=GHBooster
At $2.17 a pound, plus shipping it's a steal.
Roan