I prefer the wooden frame where you place the canvas afterwards into it but a rigid plastic liner pool will work much better than an inflatable one. I am not sure if you're a member of thegab.org, Arikun but Dataguru there uses an inflatable pool for her goldfish although she had to pull it out after it punctured. She also uses fiberglass ponds. Seatrch in craigslist for deals on fiberglass ponds.