This is just in the planning stage now, and won't happen for at least a few months, but I would like to have the plan perfected before I get a chance to make it happen. I have a small carnival goldfish, and this is a bad story, but I didn't know anything about goldfish care so he was in a tiny bowl.... for two years. Long story short, he got ammonia poisoning and I learned everything I was doing wrong, got a temporary ten, he grew another 2 1/2 inches during the first month he was in there, then three months later I moved him to a cycled 60. He was in there about two weeks then developed dropsy, so I QT'd him in a ten. However, he didn't grow anymore yet, but I'm still hoping! So this may be a 200 gallon pond for a small 4.5 inch fish, but hopefully he does grow some more. My basic plan is one of the plywood braced ones with a pond liner on the inside. What is the maximum weight these will support? I'm looking at either a 4×4 and 2 feet deep, or 8×2 that's 2 feet deep, but this may be a bit cramped. What would be the best way to build this, and which space would work better? Also, I'm open to more creative spacing suggestions, since this will end up being rather permanent. Also any plant/ substrate suggestions, or pond filter recommendations would be greatly appreciated!