so about 8 months ago, we had a marine set up, and it became an african cichlid tank. when i took it down, i saved all the sand (don't ask why, lol) and was wondering, if i rinsed it really really really well, could it be reused in a planted tank? i plan on using it for most of the foreground in my upcominf project. do you think it will still buffer the water too much though it's rinsed really really well?

What is the sand composed of?

i can't really say for sure, but probably that sea salt mix stuff.

The substrate is not going to be composed of sea salt mix. It's either going to be inert sand or some type of carbonate containing sand. The first will work the second will always be screwing with your water chemistry.

Agree with rex.

I use inert marine sand or also known as silica sand (filter sand). Most of the supply comes from around Indonesian off shore of Bangka island.

However there are other types of marine sand, such as Bali sand which is almost perfectly round but contain a lot of calcium. There is also yellowish white beach sand which formed out of lime from upperlands and broken down corals. Such sand is better avoided since they can alter water parameter too much.

Easy test is by giving some drops of concentrated HCl to the sand, if it fuzz out like soda, dont use it (a sign of plenty calcium reaction).