What is the ph of your water supply?
I use aragonite and coral in my tanks and filters and i personally don't think they buffer your water that much, they will help but its not gonna alter your water chemistry as much as bi carb and epsom will.
IMO you should cocncentrate more on KH and GH. The higher you get your kh the higher your ph will be. The higher your kh is also means there will be less chance of your ph dropping. The baking soda will raise your KH and the epsom salts will raise your GH. I have trophs and we are on tank(rain) water so I buffer my water with baking soda/ epsom salt. I find it pretty good it keeps my tank at a ph of 8 and kh 13 and gh 20 ( using api test kits). I have found that the bs/epsom won't get your ph much over 8 regardless of how much you use.
As for what ratio to use it depends what your water supply readings are from the tap. My water has a ph of 7 with kh of 7 from the tap but goes up to ph 8 and kh 13 with the buffer. I use 2 tsp of epsom salts and 3/4 tsp of bi carb per 15L. So test your water 1st and go from there.
A lot of people on here dont bother using buffers but it's easy to do once you have your recipe sussed. I fill a barrel of water and add the right amount of buffer, drain my tank and add the buffered water. It doesnt need to sit for a couple of days. As long as you dont forget to add it every water change theres not really anything that will go wrong.
Check out cichlid-forum.com or google cichlid buffer there are some good articles that will explain the advantages of water chemistry a lot better than I can.