I think I would want .20 to .5 acres for the forage pond. A larger pond has the advantage of doing double duty. If it is large enough to produce the needed recruitment of BG YOY in one cycle ... you could grow some advanced fingerling LMB over the remainder of the Summer through winter and be able to select recruits the following Spring for your main pond. Something to consider within the constraints of the topography and budget.
If possible, correct soil and location of the pond should be the first issue, second should be the layout and size, and third should be the proper equipment needed to remove and move fish carefully. If you don't have a proper sized knotless seine net, then getting a true assessment of the LMB and forage is almost impossible. If you want to have fun, then a larger pond to pull out fish with fishing rods is the way to go. If you want to bring them all up to the bank with a net and get the ability to select what you want, then stay with a smaller pond.
My hatchery pond is around 1/8 of an acre, and it's loaded with 5-7" BG that we grew from 1-2", and 30 2#-3# HSB that are ready to be seined out this next spring while the water is still cool. Maybe esshup will remember when, but several years ago I added 4-5 LMB to my forage hatchery, and they all came out at near 3# in 180 days. Volume and properly sized forage was the key.
