What's your opinion on using mussels and/or freshwater clams in the pond to help filter water?
what kind of clams are you looking at? There are issues with parasites from the clams causing problems with fish.
Parasites? Interesting. I'm not actually in the market for clams, but I read about using them and was just curious.
I have tried to keep the large fresh water clams from the great lakes region alive in both pond and aquaria and they didn't live long for me. The ponds were small so that might make a difference. Clams can filter huge amounts of water a day and can clean that water. Zebra mussels are amazing at filtering water but of course I wouldn't recommend them to you.
LOL not good. But the large native clams are pretty cool animals, just difficult to keep alive.