Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Pond full of dead fish

Went out to the pond this morning and found the entire surface of my pond, covered in dead bluegill and bass. It has taken me all day to clean the fish out of the pond. I have loaded four wheel barrels of dead fish today. My wife went fishing last night and there was no dead fish that she saw, so all of them died over night. The temp. has been in the mid to low 90s for the past week or so, maybe the heat got to them. I have an aerator that I got from Ted Lee, that I run 24/7 for the past two months so oxygen shouldn't be a problem. I noticed about 1 1/2 weeks ago that they quit eating, I feed them aqua max 600 but ran out at that time and had some game chow that I gave them. I thought that maybe they didn't like it and orderd 2 bags of 600 that will be in tomorrow. Catfish are all at the top of the water like they need oxygen and none of the talpia can be seen. I dont have a clue as to whats going on but if all goes right a fish biologist will be here in the morning to take oxygen reading to see if that is the problem. If anyone has any ideas please reply all help is appreciated.

Donnie,

I am sorry to hear that you lost your fish. That is a big fear of mine right now. It seems like my fish have just disappeared. They hardly eat the commercial food and it is really difficult to even catch a perch on live bait. I have never even seen 1 dead fish, so I guess they are ok for now.
Have you added any chemicals to your pond to treat algae or for water clarity? Have you checked your
PH? I wonder with the high heat if your pond flipped and all of the toxic water on bottom came to the top. I am speculating, but a professional
will help you pretty quickly. Good Luck getting answers. Let us know what caused the fish kill, so maybe you can that from happening someone else.

Donnie - It sounds like a dissolved oxygen problem to me. Bob Lusk recently wrote that practically all summer fish kills are dissolved oxygen related, but I cannot locate that quote righ now. The fish kill definately was not a "too much heat problem" or else just about everyones fish in your area would be dead. Neighbor's ponds will be a similar temperature as yours and they likely do not have lots of dead fish. However high air/water temperatures probably played a part - see below.

Your situation is a good example why a bottom aerator is not 100% effective at preventing a fish kill due to a dissolved oxygen shortage. There are special or unique situations where certain pond conditions will even overwhelm an aerator and a DO loss occurs. Dissolved oxygen does not have to drop to 0. A DO decrease below 3 or 4 ppm (mg/L) will cause fish deaths. Small fish tolerate low DO better than larger fish. Catfish and especially bullheads have highly vascularated air bladders and can obtain a small amount of oxygen from atmospheric air by gulping air at the surface which is no doubt what the catfish were doing when you saw them at the surface.

Numerous situations could be the cause for the DO shortage. 1. Aerator is undersized. 2. Aerator is only mixing a small percentage of the pond and a section of the pond or unmixed region will lose DO and a partial fish kill occurs. Partial can be any amount from 1% to 98%. 3. An algal bloom grew out of control and too much algal and or rooted plant biomass developed. This over bloom problem often happens in fertilized ponds. This in combination with very warm water, that does not hold a very large amount of oxygen even at 100% saturation, can result in not enough DO to sustain the fishery during the entire dark period. 4. A heavy algae bloom crashed i.e. water went quickly from greenish to clear or brownish. A crash of an algae bloom quickly absorbs a tremendous amount of DO esp at night; more than a bottom diffuser can replace during darkness. 5. Weather conditions such as one to several cloudy days with a heavy bloom causes less than optimum production of DO during daylight and DO becomes too low at night. Again, this usually happens in real warm water temps.

Your pond could have developed a toxic algae bloom but I seriously doubt this since you are in KY. I have not read where KY waters are experiencing any outbreaks of toxic algae blooms.

Let us know what your visiting fish biologist has to say after his DO test and visual examination. Note - DO conditions in the surface and near surface waters can go a long way toward recovery after 24 hours and a day or two of sunny weather. It all depends.

Probably oxygen depletion, and always a major disappointment when it happens. If you happened to take a picture, send it to the Pond Boss office; Bob Lusk asked for a picture of a fish kill about a year ago.

Sorry to hear about the fish kill, Donnie. I had a partial kill last year after an algae bloom die-off. I lost about 15 LMB(1-3#'s) and some very large CNBG(50+)........... I had bottom aeration(2 diffusers) going at the time, but it was not enough to replace the DO loss. I have set up an emergency horizontal aeration system to supplement the other in case of another DO crash in the future. One fish kill is all any person should go through in one lifetime.

I appreciate all the reply s, and I will keep you guys informed on what the biologist comes up with. I never thought about taking pictures, when I saw my pond this morning I was confused as to what had happened and I knew I had to get it cleaned up as soon as possible, pictures never entered my mind. Thinking back around a week ago I remember that a dark blackish color was merging though the water, similar to how aquashad spreads, when it is first added. I dont know what it was and still don't, maybe that had something to do with the fish kill. Will bring this up to the biologist tomorrow. Thanks again for all the reply.

If it was a low D.O. situation (which it sounds like), I would be interested in knowing how large your pond is, avg. depth, and what size aerator you have. IF your aeration system is undersized, perhaps others can learn from it. Another member indicated that he had a partial kill even with an aerator. I'm really curious to know what your turn-over rate is with respect to your aeration system. Assuming you did indeed have an oxygen crash, you would hate to think that the expense of an aeration system didn't prevent the problem. I hate to hear that you lost your fish, but I hope we might be able to learn from your situation. Thanks for your post. Shawn

thanks for posting this donnie, and very sorry to hear this news.

i'm with shawn wanting to know some specifics about yer pond size so i can learn more about my situation.

i have a shrinking pond due to hot dry CA summer conditions and no supplemental water. it goes from about 1 acre full max depth 15 ft in spring, to probably 1/2 to 2/3 acre, max depth 8 to 9 foot by fall. the pond contains alot of fish now. i definitely face potential problems with decreasing water, increasing biomass. i aerate with two bottom diffusors from 1130 at night to 0730 in the morning. so far so good.

Donnie sorry about your loss. Could you estimate how many pounds of fish you hauled off and how much is left. Just guess. Also tell us what you stocked and when. The reason I ask is ponds with large fish populations (lbs per acre) are more likely to have problems like yours. The closer a pond is to an aquaculture operation the more likely that a problem will occur. We have to remember when stocking and harvesting fish to account for growth and reproduction in the system and subtract harvest and natural morts. See these excellent links - Good for all of us to review them.

http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=6;t=000162;p=1

http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=22;t=000004

My pond is a little over 3/8 of an acre, the system I purchased below is rated for up too a 1/2 acre pond, should have been large enough for mine.

The ForeverGreen Economy Aeration System 1 comes with 1 Vertex CoActive Airstation

This system includes a Thomas single piston pump, 1/7 HP 115 v, 1 phase Wob-L piston type built for continuous use and equipped with a thermal overload protection. Heater hose, air filter and a liquid filled pressure guage are included.This system is ideal for small ponds up to ½ acre requiring up to two turns per day based on an average depth of 12 ft. This unit draws 285 watts (3.6 amps) and produces 1.22 cfm.Pump can be placed up to 2000 ft from pondside. Pressure is rated to 50 psi, (average pond depth of 12 ft will require only 6 psi) Weighted tubing sold separately

I was told that this system would turn the pond over about twice a day. The results from the biologist are 1.75ppm DO reading. He said they should be around 7ppm and that anything less than 3 is a sure fish kill. Water temp at the diffusers were the same top and bottom. His suggestion was my system is not large enough and I should imeditley get a pump and start pumping water from the pond into the air to quickly get the DO level back were it should be, and than purchase or add on the my present system. Bottom line was I will loose all fish if one or the other is not done quickly. All catfish are still staying on surface for oxygen, and the talpia are now dying. So off to Lowes I guess to get a pump after work.

Donnie, I think what ewest might be saying is that perhaps you just have too many fish in the pond, thus making the aeration a failed effort.

Big difference between recreational ponds and aquaculture ponds.

I believe the general consensus is that Ted Lea knows his stuff, so there are probably other factors, and looking at the pounds of fish per acre is a good starting point.

Donnie, sorry to read of your situation. I have gone back over the sizing specs that you provided last March 14th and will share with the group.I also have a call into you to go over this and should of talked to you by the time you read this. Your 185 x 75 oval shape pond would be 3/10 acre maximum, the water depth calculation supplied was 7-9 ft deep and I used an average depth of 6 ft even with your steep sides.The pump you have is a Thomas piston 1.5 cfm and is a slightly larger pump than the Econo 1 version we use when the pump is located pond side, this pump was used as it was to be located approx 150 ft from the pond. With an average depth of 6 ft and for this example lets round it up to an average of 8 ft to be safe you would have 780000 gallons of water and with a Vertex Coactive Airstation in 8 ft of water @ 1 cfm (yours would have more than 1 cfm) the lift would be 2300 gallon per minute or 3.3 million gallon per 24 hour day or 4.2 turns per day or just over 2 turns per 12 hour session.I also see in my notes that your water source is runoff from a neighbor that has 25 head of cattle and also the underground drainage goes into your pond.Since you are aerating and the DO was that low I am suspect that a planktonic bloom dieoff may have happened.Four turns per day is a lot of aeration and if a die off occurs turns of ten times this will not prevent a DO crash.Lets try to come up with some additional information to prevent this from happening again.Since the water temp was the same from top to bottom this indicates we have plenty of lift but something is crashing your DO when the reading is 1.75 as often I find that level without aeration.Did you do a check for DO in the top 6 inches as it should of been 70-100% saturated, if not very high in DO another indicator of an extreme demand out stripping the supply.Concentrate on the top two feet of water with anything that will splash (a lot)until the demand goes down.

PS As far as a fish load my notes indicate this pond was stocked in the spring of 06 with 50CC 500BG 12 LMB and 25 RES and 1 grass carp > Ted

I wonder if we know the size of the bluegill when they were stocked in order to guess if they spawned in '07. Same question for the (25) LMB.

The bluegill stocking seems to be about 1,750/acre if you include the RES.

If a spawn was pulled off, there could be a lot of fish in there.

Donnie can you confirm that was all the fish that went in. Ted you did not note the tilapia. Those fish numbers at 14 mths old should not fill 4 wheelbarrows (excluding the CC). Sounds like a mystery in the works. I wonder what the dark black color was?

Good point, ewest. I shouldn't have attempted to paraphrase your comments.

Eric, I was just using my notes on the stocking and all of you bring up great points, I have a call into Donnie but he is out at present, The lifting numbers I provided are conservative as the pond is oval and I used a rectangular formulation, also the turnover is an avearge as is less as you get away from the diffuser(still plenty) which means upwards of 5-6 turns at the diffuser and less as you go out from there,The boil at the diffuser would be huge within a 12 ft area at that 8-9 ft depth with plenty of water contact to atmosphere. If I would of had a smaller system at the time I would of gone with that as this system is "plenty" for this pond.Things happen faster in small ponds both good and bad.Smaller ponds can be tougher to manage for this reason.I wish the visiting biologist would of got into this deeper as to say low DO is just the starting point to understanding the problem and not to mention the cure.If I remember correctly the lake at which we had the meeting at in Atlanta had a crash from a company putting phophates in the lake (by mistake) and causing a huge bloom and die off with a lot of dead fish if I remember Greg Grimes telling the story. That lake hade a huge surface area by comparison. If Donnies situation was dead fish normal DO then something toxic would be suspect and with that low of DO it had to be getting used up very fast as should of been in the 7-8 range. I work with a lot of similar ponds with very heavy fish loads and dont have DO's below 6 most of the time and this is measured at the bottom and the level will increase to 7 plus as the probe is pulled to the surface. I normally have 90 110% (windy days) at surface to 6 inch depth.

Donnie - Note if you had a rain event near the time of the dark color moving through the pond. There could have been an infusion of high DO demand water from the cattle area. Ref: Ted's note: "I also see in my notes that your water source is runoff from a neighbor that has 25 head of cattle and also the underground drainage goes into your pond."

Things to remember.
1. Water that is warmer holds significantly less DO (100% saturation) than colder water. Example DO is 100% saturated at 11.0ppm and 50F. At 90F 100% saturation of DO is 7.4. Hutchinson (Treatsie on Limnology Vol 1) mentions that the dissolved oxygen loss rate during an algae crash can CONSUME DO at the rate of 1.27 ppm/hour (16.5 ppm over 13 hrs). If Donnie's pond was 100% saturated at 90F and DO was at 7.5, it would not take long of for the DO to be exhaused once the daylight diminished. If the previous day was cloudy Donnie's pond may not have had 100% saturation of DO the day before the fish kill.

2. If Donnie uses blue dye then the pond likely was not saturated with DO. Blue dye supresses photosynthesis in the deeper waters and production of DO is always less than "normal" throughout the illuminated zone pond.

3. There are charts or data that indicate how much DO a Vertex (small pore bubbler) diffuser will add to a specific volume of water per hour based on air flow to that difuser. We also should take into consideration that temperature of any test data may be differernt than what occurred in Donnie's pond during the fish kill. Oxygen's ability to dissolve into water changes somewhat with temperature.

Ted Lea may be able to supply some data for us regarding the DO infusion rate into water from a specific size of membrane diffuser receiving a specific amount of cfm of air. I can look some average values for this up if necessary. Ted or Carry Martin may be able to find it faster.

It is important for readers to REMEMBER that the main purpose of bottom diffusers is to mix large amounts of water and not cause oxygen to dissolve into water to a large degree or in large amounts from the bubbling action. The intense bubbling at the surface can be deceiving regarding addition of DO. Oxygen dissolves poorly and slowly into water compared to the gasses of carbon dioxide or hydrogen sulfide. Oxygen is not very soluable in water, AND air only contains abt 20% oxygen, thus it takes a lot of repetitious bubbling or agitation to infuse lots of oxygen into water. Bottom aerators are poor emergency aerators. Surface splashers are good emergency aerators for the area surounding or near the mechanical mixer. This is the reason for BarO's above comment of "I have set up an emergency horizontal aeration system to supplement the other in case of another DO crash in the future.". Bruce Condello, Cecil Baird and others also have emergency aeration available in addition to bottom aerators.

I wonder if the "black color" was the change from a pea green(good bloom) to a dark color caused by the plankton bloom die-off? I don't believe an aerator can take the place of Nature's DO producer .... the aerator may be the only reason their are any fish left alive.

Donnie wrote that " dark blackish color was merging though the water, similar to how aquashad spreads, when it is first added". To my knowledge, a crash and death of an algae bloom does not move or proceed through the water similar to diffusion or movement of blue dye. Donnie's description may not have been exact and the pond could have just changed from a green to a dark color? Everyone perceives an accident differently.

Just got off of the phone with Donnie, I think the mystery may be unfolding. I ask Donnie to post in his words the converstaion we just had. He is headed to Lowes for a pump at present.Fish load (especially the tilapia) feeding schedule and a corrected stocking date and catch and take schedule may come into play also.More to come.

Thanks Ted. My guess was fish/nutrient load and possibly some sort of concentrated farm run-off/infusion ( black cattle waste). With the aerator running and the fish doing ok one evening and dead the next am indicates that something used up a lot of O2 real quickly over night. Unless there was a cold rain or spraying weeds or cloudy weather or the like there should not have been a plankton crash. Something caused a spike in BOD (or reduction of available O2) which could not be met even with aeration.

O>K> guys your scaring me.Should I use well water or pond water for emergency areation?

Went to Lowes after I left work to get a pump to help get oxygen in the water, but all they had here in London,Ky was small sump pumps (will they work). I will try to give as accurate info as I can to help you all help me. The stocking rate that Ted Lee posted early is correct, and the date of stocking I thought was 05 but it was 06. All the BG RE C/Cat Bass were bought off trucks and there sizes were regular 3-4 BG 6-8 C/Cat 4-6 Bass. I started feeding them as soon as they would eat pellet feed that I got from tractor supply and feed them a few times a week. As they ate more I started feeding them 6 days a week, then I up it to twice a day 6 days a week. All was well and the fish grow considerably by fall. This spring I switched feed and fed them Aqua Max 600 and still fed them twice a day 6 days a week. This spring I purchased 25lbs of talapia at around 1/4lb each, which I figure was around 80 to 100 talapia that I added to the pond. I had a bad case of floating algae that covered my pond and I waited for the talapia to eat it but they never did. The algae problem got worse and my wife and I made the rope and plastic tie gadget that was posted here and dragged it across the pond several times. We removed a complete truck bed full almost to the top of the cab. I then sprayed curtine plus around the pond banks as an extra measure. That was a couple months back and the algae never has come back. Also this May early June we had a very hot and dry spell and my water level dropped 3 1/2 feet which is a lot considering my pond at the deepest part is around 8ft. Still the fish were doing fine and we fished it every other day and saw no problems. It stayed like this until the latter part of July when we had a huge rain and it filled the pond in a couple hours. Then a few weeks ago I ran out of Aqua Max and the feed store had to order it on the next order, which they said would be a few weeks. I had a bag of game chow that I had purchased but never used so I started feeding them that, which they refused to eat. I still gave it to them twice a day and twice a day they would not eat. So a few days back I quit feeding them and was waiting for the 600 to come in. This is the time period that I saw the blackish color in the pond that I have no ideal what it was.
The runoff that goes in my pond is from a neighbors pasture, this runoff is all in corrugated plastic pipe (3 sections). His pasture is hills and then slopes to somewhat flat ground. These pipes start at the bottom of the hills and tie into one at the end of the flat section at the road.The water then continues under the road by way of an open culvert, then back to corrugated pipe to my pond.
I have (had) some good size fish in my pond, large C/Cats, very large BG, and a some decent bass. I wanted to wait till next year before I harvested any of them, so I haven't taken any out, all are still there except what few has died naturally. I have had all species spawn and had plenty of offspring's. This could be my problem too many fish not enough pond.
I don't know how many pounds of fish that has died, I hauled them off in a standard size wheel barrel filled about half way up, did this 4 times last load may have been smaller. I have lost 8 catfish and 2 talapia today and am sure the rest will die if I cant find a pump tomorrow, still may be to late. I am sure all the BG and Bass are gone, my fish population is totally wasted. I still have plenty of fry that seems to be doing fine, I can start over with them hopefully.
I know this has been a lengthy post, but if anyone can use any of it to save their fish then it was worth writing. I totally believe I created this mess myself by thinking I could over populate with aeration and hand feeding. Don't make the same mistake as I, keep your numbers in check. Thanks for all the information, I will know better next time.
I would appreciate information on a pump. Will a sump pump work if not what will.
Thanks

Donnie, I'm sorry to hear about the fishkill. It sounds like the well-fed fish and drought-shrunk pond constituted 20 pounds of stuff in a 5 pound sack.

I would grab a sump pump if that was all that I could find and pump the pond water up to splash back in on itself, at least. Someone may have a much better idea.