LMB are hard to sex for even a pro. Not sure if you could get same sex LMB from a hatchery? Guess that would depend on hatchery...
Females in most caeses will get bigger than males. Either one will get decent size in your pond. Say 2 to 4 pounds if there is enough food. The problem you will run into is you will more than likely run out of food for them to eat sooner or later. They are eating machines! So you will have to fish the out at some point once you think your pond is good to go goldfish and leach free!
Most times you can judge what a bass will try to eat by 1/3rd its size. So if you have a 15 inch bass it will (try) at times to eat a 5 inch fish depening on the size of the 5 inch fish.
I posted on the other thread already about the bacteria.
RC
I thought they were difficult to sex. I guess my two main concerns about LBM then are first that they would over populate the pond eventually. Maybe they eat their young though? Second, I also worry they would wipe-out the frogs. Many goldfish are too big to be consumed by the bass so I assume they would continue to breed. Which means food for the bass as long as we keep their numbers down.
Thanks for the info on the bacteria. I will check the stuff out that you mentioned. I know we need to aerate but the systems are expensive. I'm not sure when we'll get one.