I'll check home depot tomorrow for the grey sand. My local Lowes only had beige sand.
I have only seen the grey Quikrete Play Sand; members elsewhere have mentioned the beige/tan. I like the dark grey, it lightens up under water and tank lighting, but very authentic Amazonia stream sand in appearance.
I looked around at a local landscaping yard for river rocks. When I mentioned this to my friend, he warned me that some rocks can affect the alkalinity of the tank and sent me to YouTube to find out how to test rocks for safety... Now I have a gallon of muriatic acid, lol. That's the only size Lowes sells.
Calcareous rock will slowly dissolve calcium, raising pH and GH. River rock is generally safe, but I buy mine from a local landscape outlet. A pail is 75 cents, and it comes in various sizes so you can get a nice boulder and pebble effect, very natural. This is the rock in the photos posted earlier. Be careful collecting rock, it can absorb any liquid it comes into contact with. River rock is rock collected from a river that has been tumbled around for hundreds of years.
Aside from scrubbing and boiling driftwood that I find, are there any other safety precautions I need to know about using found driftwood in my aquarium?
Wood has a real risk, much worse than rock. Collected from water is probably safer respecting toxic substances soaked into the wood, but then you have the risk of water pests. Temperate fish diseases are different from tropical fish diseases and pests, and tropical fish do not have any immunity to temperate fish issues, and vice versa. But if you still want to risk it--it must be hard wood, meaning oak, beech, etc. Soft woods generally rot rapidly. Coniferous wood is soft but more importantly often highly toxic. I had a chunk of cedar many years ago, purchased from a reliable fish store too, and after a few months fish started dying. Finally traced the toxin to something seeping out of the wood, with the help of a professional biologist/aquarist. I do collect branches (oak, maple) but my larger wood is Malaysian Driftwood from fish stores/online.