Yes, an aerated pond can support more fish.

Yes, 20 feet of depth, if all aerated, or usable, by fish would be really nice.

Yes, Good slopes help to "manage" rooted plant growth.

I've got 2:1 slopes around my favorite little pond, and the rooted vegetation only grows out about six feet. I know that's a severe slope, but it's working great for me.

Correct me, Sue, or any other aeration experts, but the twenty foot depth would likely require a significantly bigger pump, than one that would be appropriate for twelve feet of depth.

Holding a redear sunfish is like running with scissors.