Was walking the pond tonight and noticed a white object in the pond so I went to check to see what blew in and to my surprise it was pure white gravel in a circle about 8"-10" in diameter. Having only owned this pond for a year I've only ever seen leaf litter on the bottom but my bluegills apparently found gravel under the leaves. I'm guessing when they built the pond (dug and ground water) they lined it with gravel so I'm hopefully that my diffuser is doing the job of reducing the amount of organics on the bottom as it looks like they didn't have to go far down to find the gravel. I've also cut all the small trees around the pond and several over hanging branches to reduce leaves and allow sunlight in. I caught 2 females loaded with eggs last week and have left the pond alone since for them to take care of business! Hopefully with the full moon this week we will have our first successful bluegill spawn in our pond!