Hey Bob,
Check out this link for types of fish you are likely to encounter.
http://www.dnr.cornell.edu/Sarep/fish/fish.html If there is no wild water running into your two ponds it likely what ever is in your pond was put there by someone. And since your goldfish went crazy multiplying, I'm guessing there was no significant predator fish in your pond. Look at the yellow perch and pumpkinseed/red breasted sunfish pictures.
I have read that bass will eat leaches. I expect that is a statement about small bass. 10in bass are looking for a larger meal.
A pumpkinseed sunfish is said to eat leaches. It is related to the red-ear or shellcraker (sunfish) and will eat snails and leaches off the bottom.
The only thing a bass won't eat is something to big for its mouth. Very large bass will eat other smaller bass. So unless there are big pike in your pond (very unlikely), in a few years provided lots of forage, grandma bass will without hesitation eat the 6-10 once bass. She will also eat ducklings, mice, frogs, or anything else given the opportunity.
So the bottom line for your question for survival is “yes.” Just make sure that pond has plenty of sunfish for them to eat.
