I've heard several talks about how sand for substrate is a bad idea due to some chemicals building up in air pockets. I'm wondering if I should be worried in this case. I purchased a banjo cat and saw someone post a photo how they had made a small spot for the banjo cat to burrow into some sand since that is what they do best. I have rock substrate in my 36 gallon and there is no way he could burrow into it. I have a 6" terra cotta flower pot base (the short piece that is like a dish) and plan to add regular old tan colored sand and bury it to the rim in the substrate so it is just a round circle of sand for him to burrow in. the sand will probably be no more than 1" deep 6" circle. Would I be likely to see a problem with this? I doubt I will vacuum the sand and I don't want any chemical problems because of this. Kyle