I am planning on making a mini bog in a very ornate (read...very expensive) 18” x 15” x 4” Japanese clay bonsai pot. I filled the drain holes with Poly Seam Seal and made provisions for a drain hole that can be opened. My plants (VFTs) would stay in their plastic pots, set in the bonsai pot with peat/perlite mixture and a ½” of water. I have read that using an unglazed pot is an absolute no no. What is the reason for this?