Hi Ron,
Have you looked at the odyssey muck vacs at all. I may have missed something in your earlier posts but if you have decent water pressure from a garden hose you can pull some light stuff up with this without disturbing too much of what you want to keep at the bottom...snails, rocks, etc. But it will work well on light muck and debris. There is a discharge hose which you can put a mesh back over (something like cheesecloth) and strain the debris out and just run the discharge hose back into the pond. The same would go for any of the conventional pond vacs, like the pondovac 4, matala, etc...those that have discharge hoses could easily return water to the pond
Shop vacs of course don't do this, but they can be helpful if you don't have a lot to pick up.
Finally the other thing about the pondovac...it has a lot of different nozzle attachments so you can pick a really narrow one to limit how much you suction up. The biggest problem I've found is getting the right fit for what a person has at the bottom...some powered vacs are really powerful and you don't want to pick up too much, but by the same token for people trying to remove leaves, you have to have some decent suction.
Best wishes to you on this!
