Am planning a shallow wading pool type pond for my tortoise enclosure - must have easy access and be shallow, and easily cleaned. I'm in southern Cal, so a nice warm climate. Any advice ? Can I just dig a shallow gradually sloping hole, put in a mold of chicken wire, and pour cement ? Thought I'd either use a drain in the middle or a sump pump to get the dirty water out. Flexible liners are an option but they get so hot in the sun that I worry about the tortoises sitting on them.