I felt like this was a good time to post some info on FHM and their spawning behavior. Many recent postings leave the impression FHM have spawned "once or twice" now. I will try not to drag this out so bare with me here.
First, FHM become sexually mature fairly quickly at an intermediate size-not just as 3 to 3-1/2" adults. Males are slower to mature than females for a reason.....stress or lack of. Males begin cleaning rock, wood, pvc pipe or actually about anything intersecting the basin.
He attracts females to continually lay eggs in his spot. He guards, cleans and hatches daily until death.
The part that is sometimes hard to understand is the frequency of the spawn as a group. They do not actually spawn as a group, they spawn as individuals which means there are females laying eggs every minute of the day when water temps rise and they are triggered to spawn. Every minute of every day for the summer months-generally. When this is happening, keep in mind there are eggs hatching every minute of every day, throughout the summer. Every day the FHM are growing in numbers substantially higher than mortality.
In a fertile environment the first 30-60 days of hatchlings can become sexually mature and begin the cycle the same as the original adults did-in the same year they hatch. This is a part of the reason starting in a new pond it is not necessary to pile an outlandish number of minnows to start, in fact it's best if you start with a lower number so the forage (planktonic in nature) available to the new hatch is not removed too quick-fertilization is important here, or having the nutrient load available to grow the single cell organisms that start this cycle.
I have seen several project beginnings with my own eyes where the FHM and GSH have started to appear very lean due to a lack of fertility. A fish eating 100 skinny minnows is getting far less return than a fish eating 50 fat, healthy minnows because that fish done twice the work for the same useable consumption so the higher the reproduction, the more fry, the quicker this can occur, creating a problem that is not easily corrected. To add to that, it's not always practical for some pond owners to fertilize at the right times with the right products simply because "they didn't know". We hope they all find PondBoss to gain the knowledge needed, but we've all seen that at some point because we didn't know what we didn't know...
I hope this makes sense and isn't misleading to anyone, I have just noticed several posts this spring about FHM that waved a flag for me. Hope this is useful to some.

Well said. After my initial stocking, I haven't even tried adding more FHM for the reason you mention. GSH, TFS, TP, RBT do more for bass growth.

Well said Snipe.

I have a one acre pond with Fhm and GSH I stocked Rbt to have something to feed and watch the water is very clear but slowly starting to get a bloom. I built what I think of Fhm breeding hotels it is plastic(cardboard) cut into 8x8" squares and stacked on four pieces of quarter inch all thread with about two inches between layers(six layers) and stick the ends of the rods into the bottom in the appropriate depth. I placed several next to a retaining wall that is by my front porch so I can sit in my reclining chair and watch the action they seem to be working great I see males setting up on each layer and I can place them about twelve inches apart and they seem to work their specific layer without trying to chase others off

It's amazing how many fry they can produce in a short time. I have since stocked BG and Res . My supplier told me they were between one and three inches when I got there to pick them up I found that the size was probably one and a quarter inch max they are so small that I can't get them to take fish food yet even if I grind it up to my it smaller. So hopefully with lots of Fhm fry being produced they will have plenty to eat

BG/RES at small sizes can do quite well on aquatic insects/inverts and other organisms too, they will however utilize FHM fry as well.. you should be in good shape.
Hate to hear 1-3" fish averaging 1.25" or mostly less than 2", but I will say I had a customer that wanted 3-5" BG. I hauled to him and as we were stocking he mentioned they were too small. I stopped, pulled my board out and said here, take any fish you want and measure it. He found quickly that my 3-5" BG were mostly 4.5-6" BG.

Funny how they always look smaller than they measure

I wish I could buy from you but I could have put all 150 BG in a quart baggie with room to spare

The males also change color when spawning.
Eggs above male in second photo

FH hiding

Will FHMs wipe out the FA in a newly renovated pond?

I ask this because my wife and I can't put our finger on what has removed all of the FA we had on our pond this Spring but what looked like it was about to get away from us has now reversed course and we see absolutely nothing and are loving it.

There are a lot of potential variables involved in tackling the FA, we took a number of actions, but I am just asking about FHM since this is a thread about them. We put about 5.5k FHMs in our about 2.5 acre pond in April. We also stocked BG, RES, 100 CC and 100 2-4" LMB. Our FHM population has exploded in that short amount of time. I really thought the LMB might wipe them out but there are schools of new minnows every step of the way around the banks of the entire pond. It looks like millions to us but obviously not, at least tens of thousands though. I don't fear that the FHM will disappear anytime soon, at least not this first year.

So, is it possible that the initial 5.5k and all their tiny spawn could have been a significant enough influence in the rapid decline of our FA to pretty much zilch or would they have a negligible or zero net effect most likely?

Did you stock crayfish? If not, you might consider it. They will consume a lot of algae.
I've not needed to treat FA growth for the past two summers, and it's looking like I won't need to treat for it this summer.

I kind of miss the 3'-4' visibility, but in exchange for the disappearance of FA, that's a good trade.

I was planning on putting crayfish in my pond when the algae started coming on strong earlier in the Spring. Now that I see no algae at all I don't feel a desire to. My water clarity is pretty good too now that the dye we put in early Spring when trying to combat the algae has faded/washed away.

After my last post, I walked down to my dock to throw some worms to the bass and bluegill that hang around the dock. I walked a little bit on the nearby shoreline to look at the FHM swarms again. The numbers of fry are staggering. It really does look like there must be a million in this pond but I would think that has to be impossible seeing that it hasn't been any more than 8 weeks since I stocked them.

It's amazing how fast they reproduce. I built spawning structure for them basically eight by eight inch squares of plastic cardboard set on four rods with about two inches between layers each layer has a pair spawning. It seems like a finished hatch every day the fry are growing fast even though my water is really clear

The structures in my lake are my dock, several brush piles of mostly dead cedar, rocks of all sizes, and then a few pallets I stacked up in two spots. I was worried I didn't have enough at first, not knowing how well what rocks and gravel we have in there would have worked.

Yeah, they spawn like crazy. I wonder how long it will take these fry to start spawning and if some of the first spawn have already started breeding. It's been no more than 8 weeks since they've been introduced into my pond. This is all new to me but I am tickled silly with what I'm seeing in my pond so far since it's filled up.

Judging by the size of my fresh fry they look like they are about a month away from spawning they are about 12 weeks old right now but I think they had a slow start when I put the parents in I had 13-16' visibility. When the new ones start to spawn it is going to be amazing to see how many show up. I have since put in BG and Res so there will be a ton of fry for the sunfish to feed on

Once you can walk across your pond on the backs of the FHMs, then it is probably safe to start stocking your other fish!

Probably not... In fact it can go the other way if FHM consume large amounts of zooplankton-which consumes the phytoplankton.
The swings from algal growth to clear water is pretty normal the first few years of a new pond at our latitude. There are lots of changes taking place as the ecosystem builds and balances.

^^^ What he said. The other thing that can make FA "go away" for a short amount of time is a heavy rain. It beats the gasses out of the FA that is making it float and it sinks to the bottom.