Pond question

[sawtooth]

Hello friends,

I recently had a pond management service come in and spray one of my ponds for duckweed. They told me the chemical was harm harmless to wildlife but within about seven days after they sprayed the pond now has hundreds of dead bluegills all around the edges. Obviously the chemical had some affects but is this normal? I’m going to call him today as soon as he opens up I’m trying to figure out what’s going on. My guess is they either ate the duckweed and it killed them or since they were bedding and the duckweed was over top of them maybe had some effect since it was around the edges where they were on their beds. Thoughts?

 

[East30]

Could be an oxygen depletion issue. Duckweed and other possible plant life dying using up oxygen in the decay process?

 

[oosik]

If it were an oxygen issue you should have seen hundreds of bluegill surfacing and "air breathing". This would have been a day or so BEFORE they all died.

Did it actually kill the duckweed? Have you seen any live bluegill?

Experience would show - it's almost impossible to rid a pond of massive weed growth without affecting other pond inhabitants. What about your frogs - flying insects - crayfish - ??

 

[sawtooth]

It’s not oxygen but good idea. Only minimal part of pond was covered with duckweed just trying to stay ahead of the game. I’m going to look again but only bluegills dead that I can see. Nothing else so far. All fish died within a 3 day period too.

 

[oosik]

Sound to me like - the chemical used or the concentration used. Ask what was used and at what concentration.

 

[rekees4300]

Thoughts?

Instead of using chemicals to control weeds get some sterilized Grass Carp. My 1 acre pond was overrun by weeds for 15 years. Five years ago put 12 small Grass Carp in there and 2 years later they grew from 10 inches to 2 feet. Now ALL of the weeds are gone, even Cattails!

 

[MoKelly]

Instead of using chemicals to control weeds get some sterilized Grass Carp. My 1 acre pond was overrun by weeds for 15 years. Five years ago put 12 small Grass Carp in there and 2 years later they grew from 10 inches to 2 feet. Now ALL of the weeds are gone, even Cattails!

This is the answer. My neighbor did exactly this in his 3 acre lake an the results were amazing. They grow into big fish!

MoKelly

 

[sawtooth]

I actually just did this in my other pond I put in 40 sterile grass carp the same week I did the chemicals in the first pond. I used chemicals in first pond because I was told the grass carp couldn’t manage the duckweed. Wishing now I would’ve tried the carp first.

 

[ponytug]

FWIW: Grass carp do eat duckweed, it just isn't their favorite.

I hope that your pond recovers.

All the best,

Peter

 

[Jstpssng]

Just curious, what pesticide did they spray with?

 

[sawtooth]

Guy called back and said he spoke to the kk chemical rep. Rep said that was extremely uncommon and that he felt the pond was way over stocked with bluegill or the fish were at a certain point in the bedding process that they wouldn’t leave the beds after all the chemical was applied.

This is what I think may have happened. Service provided used correct amount of chemical for pond size but chemical was applied primary around the shoreline where the duckweed was concentrated vs spreading it out evenly across entire pond. Considering bluegills on bed at shoreline with high concentration of chemicals and duckweed I think maybe been what caused issue. We’re trying to determine now if any bluegills made it or if we need to restock. I’m done with chemicals now though.

 

[buck12]

I am no expert on pond management. We live on a shared 2.5 acre pond. My neighbor who is retired takes care of it and I pay him for my share. Every few years we get some type of vice like stuff that grows in the shallow areas. I do not remember the name of it.
When he sprays, he does a section at time. He said if you do the whole pond at one time it removes too much oxygen. I have no idea if he is right but we have never had a fish kill.

 

[check]

Wow, I guess I am lucky. No weeds on my 6 acre, 50 ft. deep pond, and lots of oxygen for the rainbow trout that I stocked it with. Only problem was, the killer Merganzers!

 

[sawtooth]

You must have a good strong stream or river flowing into that pond. Anything over 12 to 15 feet wont hold oxygen below those depths unless you do or have a aeration system.

 

[oosik]

My pond is ten acres. Five of open water - five of cattails. It's 80 feet deep - 45 feet deep where the water contacts the basaltic lava side walls. I have dissolved oxygen to a depth of about 65 feet. Below 65 feet it very quickly approaches zero. It's fed by very large springs on the near end. It's had most every type of trout and two species of salmon in it over the years. Now it's bass because they will spawn in a closed lake environment. In the late summer, surface water temps will reach 62F - 56F or lower at the thermocline. Picture of my lake, taken off my front porch.

 

[LD1]

What was the name of the chemical used as I am curious?

I have a ~0.85 acre pond.....bout 8' deep. Its a 70 year old farm pond. Has always had issues with pond "weeds". Never an algae problem. The pond as always had grass carp. As a kid I remember seeing them and they must have been 4' long.

Fast forward to now, I have owned this place for 6 years (I grew up next door and always fished this pond as a kid). I re-stocked with a dozen 10" grass carp. In two years they were 2' long but still a weed problem every year.

I pulled some weeds to identify....had 3 kinds. Coontail, water milfoil, and cury-leaf pond weed.

I made some calls and the consensus was that of the 3.....the carp would only control the curly leaf pond weed. So I switched my method to chemical. I use diquat. Alligare Diquat Aquatic Herbicide | Solutions Pest & Lawn

I mix half the gallon in my 4-gallon backpack sprayer and walk around spraying about half the pond. Wait two weeks then do the other half the gallon. In two years.....no fish kills and now weeds. So I can actually fish it with spinners and topwaters not without constantly being in the weeds. Because the weeds would cover about 85% of the surface.

 

[LD1]

This was my pond.

These were the weeds pulled. Top is coontail, middle is water milfoil, bottom is curly-leaf pond weed (by my amature diagnosis)

And these are a few of the dozen carp after just a few years. They are even bigger now.

 

[oosik]

LD1 - have you ever thought of getting Grass Carp. The Fish & Game Dept tried them in a large lake about 25 miles south of me. They were seeing the same condition as you have in your pond. In a matter of four/five years these buggers grew to 5# to 8# and had TOTALLY cleaned out all the water weeds.

This is a really long & deep lake. Left over from the Lake Missoula floods - thousands of years ago. Rock Lake - seven miles long - - 375 feet deep.

I could get them here but pretty certain they would eliminate the five acres of cattails down at the far end of my lake. I really like my cattails and the pond weeds aren't really that bad. My lake gets too deep too fast for a whole lot of pond weeds.

 

[LD1]

LD1 - have you ever thought of getting Grass Carp. The Fish & Game Dept tried them in a large lake about 25 miles south of me. They were seeing the same condition as you have in your pond. In a matter of four/five years these buggers grew to 5# to 8# and had TOTALLY cleaned out all the water weeds.

This is a really long & deep lake. Left over from the Lake Missoula floods - thousands of years ago. Rock Lake - seven miles long - - 375 feet deep.

I could get them here but pretty certain they would eliminate the five acres of cattails down at the far end of my lake. I really like my cattails and the pond weeds aren't really that bad. My lake gets too deep too fast for a whole lot of pond weeds.

?????

 

[oosik]

OOps - missed #16.