You can't go wrong with aragonite as a gravel in your tank. Aragonite is a high calcium mineral from the oceans,has at least half amount of the natural trace elements just by itself. I'd recommend to anyone in SW "business". 1-2 lbs/ Gs of water. Do not overdose. Too much of Aragonite can be a result of way too high alkalinity and low levels of oxygen. Live sand is about the same when it's came from the right source. Live sand a bit lower in Calcium, but very good as a natural buffer. With a good water parameters Aragonite can least for a lifetime, while the sand has a 5-7 years "lifetime" It'll remain alive, but the buffering capacity will gets lower. Both, aragonite and live sand are the best substrates out there today, in my opinion. If you have a good estabilished live sand bad in youir tank right now, I would't bother to change it to aragonite.