OK guys, I'm now thinking that the best way to deal with my serious algae and weed problem is to drain or partially drain and deepen the pond. Again, this is a 4 acre 50 year old pond that has never been renovated. We're talking 2-3 ft depth at the east end moving to a bowl in the west end of about 8 ft depth. The pond is newly re-stocked but heavy FA is covering 80% of the surface. Submerged vegetation is also thick. We've tried GC in the past but it's been all or nothing with them.
I've attached an aerial view (taken in winter - the white is ice cover) and outlined the shallow area in yellow and the deeper part in red. The dam is marked in green and the position of two aerators is marked with blue.
I'm trying to come up with a way to keep the fish during the renovation process. I got a crazy idea the other day and wanted to run it past you all. Would it be possible for me to draw down the pond enough to expose the bottom in the shallow (east) end and allow it to dry out enough to deepen that part with an excavator? The fish would remain in the deeper (west) end with an aerator. Once the shallow end was excavated, cut a trench and let the water (and fish) flow into the newly deepened east end (with an aerator) and then rework the west end and dam. The middle part of the pond could serve as a barrier between the two areas during excavating and then serve as a shallow area once the pond refilled.
What do you think? Is it even possible, or way too complicated? Would the added expense not justify trying to save the fish or would it be better to just drain the whole thing, do the excavating and restock....again. Thanks for the input.
travism, that's exactly what I did when I renovated my pond a few years ago. The shallowest part is now the deepest part. I drained the pond, which forced the fish into the deeper part. I was able to make a temporary dam allowing me to raise the water level in the part of the pond with the fish. After part of the pond was renovated, we broke thru the temp dam, then worked on that area. Depending on which part you want to make the deepest, you can either remove or rebuild the temp dam. Plan on having a lot of sediment flush into the pond when you break thru the temp dam. The water where the fish were had 6" of visibility for the few months that we were working on the pond. I ran my aerator in that area, and only lost 1 BG the whole time.
It might be easier to just lower the pond level, deepen the shallow part, siphon or pump water from the wet, old deep part to the new, dry deep part, and move any fish by bucket. Cutting a trench is going to be a PITA, and the flood of water through the channel will stir up a load of sediment.
I've done something similar, siphoning down a small 1/8 acre pond, fishing the hell out of it and transferring LMB/BG by hand to another pond, then siphoning it dry and collecting any last fish by hand. If you have an open day or so, it's actually a really neat exercise, and a great opportunity to get rid of carp or bullhead.
One thing to consider: now matter how you choose to do it, this will be stressful for your fish, and your forage base may well get depleted. You might want to do this once water temps are a little lower, and throw a few pounds of GSH or something in the newly filled area to give the LMB something to munch on for a while.