I put in a dry dam on the next draw over and ran a pipe to the pond to get more surface water. Works great and has solved my filling problem as it runs a full 8" pipe when a decent rain event occurs.

That led me to think about putting a small pond at the bottom of the dry dam and raise FHM for feedstock in my main pond. When rain event occurs the FHM pond would overflow into the inlet pipe to the main pond as the dry dam fills, then flows into the main pond. It looks to me the only thing I would have to do is dig a hole and construct FHM condo, everything else is already in place.

Questions:
How large a mini pond would I need to raise FHM without restocking or much care?
Do you think the water level fluctuation would be enough to carry a portion of the FHM into the main pond.
Am I entering the lunatic fringe of pondmiestering?

I like how you think, but I wonder the same thing about the overflow carrying ample amounts of FHM's to the main pond. "Ample" would mean enough to substantially feed the main pond fish AND enough to keep the forage pond from overpopulating.

I have though about this and pondered putting the pipe in as a drain instead of an over flow and just letting the whole thing go to the main pond in the fall and restocking the forage pond with breeders in the spring.

I am contemplating this with a 1/10 acre pond because I have a catch basin of that size uphill from my pond that could easily be de-mucked and deepened. It may just turn into a seined forage pond, but a guy can dream can't he?

The problem will be keeping predator fish out. BG will swim up inch deep water. I assume YOY LMB would do the same.

I had to drain and lime my forage pond last fall because baby BG and LMB had swam up the one inch deep water from the main pond during an overflow, and had grown and decimated ALL the FHM. It's probably going to be a yearly thing if it floods in spring; pump it down to a 8 foot wide six inch deep puddle, net everything out I want to keep, and throw about 10-15 pounds of hydrated lime into it.

A few clarifications on proposed setup. The inlet would normally be above the mini pond water level. The inlet drops vertically about 20 inches then runs horizontally 900 feet with an approximate drop of 6 foot. The outlet is a little above normal pool of the main pond, but the outlet would be under water during high volume rain event. Water would run over the emergency overflow well before water would back up to mini pond level. I believe there would be no time that the 8 inch vertices pipe would be full unless pipe was full flowing into main pond.
Main pond has a 8 inch siphon overflow installed.

I had a similar idea originally for a couple of ponds I built. The upper one has FHM, and the thought was some would go down the outlet ditch to the lower pond. The pond overflows regularly, as it is at the bottom of an irrigated field. The only time I get significant movement is in the spring of the year. I’m not sure why that is.

IIRC TJ(Teehjaeh57) has a setup where he moves forage from a small pond to his main pond via a pipe and valve system. You might send him a PM. I'm sure he would be willing to provide some valuable insight/advice from his experience. Good guy and always willing to help folks.

There are pictures and descriptions of his setup somewhere on one of his threads but I don't have it at my fingertip. I remember reading about it about the time I was new to PBF. Is a great idea if you have some elevation to work with. My forage pond just does not have enough elevation to utilize gravity for harvest. Wish it did.

I have seen his setup and it does not pipe directly into his main pond but is such that he can put a tank at the end of the pipe and collect the fish. I think he used an 8" pipe to be large enough to pass relatively large YP.

During a high water event, small fish will swim the pipe up to the forage pond, even if it's 1/4 mile. Please don't underestimate the migration potential of small BG, LMB, or green sunfish.

Will the fish be able to swim against a flow like this? At the intake end there is a 90 degree bend with about a 20" vertical rise to the ground level. As the level in the dry dam section drops the flow decreases but the vertical section of the pipe isn't very full at all.

You are likely ok but never say never when it comes to fingerling fish moving in shallow water. My forage pond has about a foot of drop into my main pond and as far as I know I have never gotten any BG contamination. I'm pretty sure I will some day when we get torrential rains and flooding as when my main pond gets to flowing 10" or so over full pool and out the emergency overflow the end of the forage pond overflow will only be a few inches above and I have personally witnessed small BG jumping up 8" vertical drops of water and go between my main pond into my sediment pond.

They will swim right up the stream of falling water.

About 17 acres in main body with 5 sediment ponds totalling maybe 4 acres feeding into it. I stocked all sediment ponds with fathead minnows and grass shrimp. In some of them, fathead minnows became thick. All except one had pipe of some diameter (most 14") draining from sediment pond to main body. The dam on one without pipe quickly washed out in one spot and drained to big one. Three of others had water backup to drain pipe and fathead dissapeared. One with 14" outlet pipe about 4 vertical feet above main water body had fathead minnows longer, but they eventually disappeared too. Not sure why, but suspect predator fish got there somehow. Worth trying. I will try again at some point.

Never saw grass shrimp again.

I had a lot of fhm's in my sediment pond at one time but the numbers dwindled down over time. My only predator turned out to be bull frogs. I counted 14 at one time in this small little sediment pond. I know I lost some during high water events where they went downstream to the big pond but still I am sure the bull frogs ate a lot of fhm's. I had no bull frogs in the little pond before I added the fhm's.

I have often wondered if a small pool like a 12-16 foot above ground pool could be used along side a pond for raising fhm's. Where I am at our ponds are on the flat ground and dug down, not much of what you would call a damn. I have about 1-2 feet from drop from the edge of the pond to the water. Any thoughts on how well this may work for raising fhm??