Tracy, I've had a 1/4 acre brood/growout pond for over 3 years now, and have had tremendous production from it. I can't comment on the size, but here's my general thoughts about the pond itself.
If your big pond and this new one are at the same altitude, the biggest pain is going to be getting the fish out, so that would be one of my biggest design concerns. A paint roller tray design is basically what I did, and I had a net made that will cover bank to bank, and drag the bottom at full pool. Smaller nets mean more pulls, more trudging through the mud, and that means more work. If you look at most production ponds, they're shaped similar to a shoe box, and that allows a single straight pull. Once they're trapped at one end, you can always use a smaller minnow net to pull smaller workable batches of fish. I learned this the hard way.
Bumping it up against the big pond does make water level easier to control also. Raising and lowering the brood/growout pond is very easy, and a 2"-3" pump will make fast work of that. Since I use Honda powered pumps, and they really like to be level because of the low oil sensor, I just built a small platform so the pump is always dry, always level, and out of the mud.
Now Tracy, you're well on your way to brood/growout pond addiction. Snrub will tell ya', they're just too much fun. I actually bought this spool of Olympic lane markers on a stainless steel dolly for $100 after no bids at the monthly equipment auction. I see a blocking net in that spool's future.
Yeah, I'm addicted.
Hope this helped, Al
