There is one big problem with sand that you may want to be aware of... The fact that it starts to clump and ends up with stagnant areas that hold toxins. Because of this you have to be sure to stir it up every so often, not just the surface area. I had a aquarium with a layer of laterite on the bottom and then mixed black tahitian sand and larger black gravel. This still didn't solve the problem of the stagnant areas. The result was losing just about every fish I had despite every thing to try to remedy the resulting bacterial infections. The only solution was a complete tear down. I would recommend several layers of larger sized gravel, such as laterite or flourite or plain gravel, topped with the desired sand with a mix of smaller gravel. This will help keep down the stagnant areas. Also, sand that becomes stagnant will turn black, course this does no good to tell you when it does when it is already black. Hope this might help.
