I was recently given a 20 long with a filter and heater, along with aragonite sand and reef rock, as the previous owner was going to set it up as a reef tank. I'm wanting to set it up as a low tech planted freshwater tank (possibly with CPDs or a betta, no cichlids), and I was wondering if I could still use the aragonite substrate? I'm planning on adding driftwood, so that might lower the pH a bit, but would the aragonite cause too much of a pH spike for plants? I'm not adding CO2 and my tap water runs slightly acidic. I have had success so far with freshwater sand and root tabs in my other heavily planted tanks. I have some pebble substrate I could use as well, but I'm worried that large pebbles won't hold root tabs for stem plants. I want to try to use what I have, but I don't want to try the aragonite unless I know it is safe for my tank.