So I had this great idea hit me yesterday. My wife actually seems open to it which is scary enough as it is. I was originally thinking about a lined pond but then realized that would be difficult and figured it would be easier and hopefully less expensive to do a mud pond. My idea was to build a moat around a play castle for my daughter and future son (going through an adoption for him right now) which would double as a mud pond. What I need to know is 1. what kind of water volume would be absolutely necessary for a mud pond to how many fish 2. what else I absolutely need to ensure a healthy pond. I've seen that aeration is a big part in a mud pond and of course a way to retain water. The good news is that the property has a high content of clay and I probably won't have to add anything to it. The bad news is the property is just over an acre in total and my house is on it and my wife won't be accepting of a 1/4 acre pond, nor would my association/neighbors. I'm thinking a 5' wide moat around an island of about a 12 foot diameter, castle and drawbridge.