Pond Boss Forums GENERAL QUESTIONS Help Sudden death of a lot of fish

In a pond of 9 years the fish started dieing with no good reason. These are all feeders that I used to establish the pond, the water is aerated with a 2400 GPH pump, the reading show Good or acceptable values for Nitrate, Nitrite,Hardness,Alkalinity and PH. I just got the Ammonia test kit today and will test with that. This all seemed to be in coincidence with the new food supply from Wardley- Pond Ten, but have stopped feeding this and the fish continue to die. Three today and 7 yesterday. The strange part is that most of them are the smaller 1 year old ones. The fin condition is very good in there are tails up to 3 inches long- no spots. I have been told by a local pond builder to empty the pond and scrub it down and refill it and it seems that this is the only way that I could remove the sludge that may be the cause of this so this Sat may be a fun day- any help to fix this besides is welcome.

you didnt mention O2.....how are the oxygen levels? on the 2400 GPH "aeration" pump, this is pumping water correct? what is the source of the water?

Hi Dave,
The pump is throwing water about 18 inches into the air and landing in about the middle of the pond. It source is the strained intake at about the 8" level.
I have no O2 measuring equipment but know that the fish have never been at the top of the water trying to get air. I have seen this in some stagnant lakes.
I have two other pumps taking from down below and then dumping at about 6 " above the water line to add to the aeration pump. The sterilizer is also creating O2 as it dumps into the surface. Temp was 25 degrees C last I looked.
Thanks for your input-I know this is not easy to figure out.

Skywave sorry about your situation. You are right that sometimes it is hard to tell what is wrong. Take a look at this thread from the archives.

http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=22;t=000038

I would like more details.
1. Are dying fish bass, BG, catfish or other spp?
2. Original fish, correct? Thus they are 9 yrs old.
3. You mention 7 dead yesterday, 3 dead today. Are fish dead in the morning when you get up or evening when you get home?. Of originals how many were stocked?
4. How big is pond and how deep? Any amount of rooted weeds or FA? Volume estimate in gallons or acre ft?
5. Aquashade used?
6. Water clarity - visibility?
7. Fertilize plus feeding?
8. Any water shed supplying this pond? Recent rains?
9. Any chemical treatments in last month?
10. Pump runs 24 hrs?

Note - in my experiences rarely are pond builders experts at managing ponds and fish. It is like going to an ear nose and throat specialist for thyroid or ulcer problems, Or going to a dentist for treating appendicitis or kidney stones.

Bill, I'm sweating bullets right now on that one, details to follow later but "so far I would say so far". The horizontal aerators are running 24/7 right now and no detectable problems yet.

Skywave, do you have a good algea bloom going on right now? Followed by a strong cold front, rain, and lots of cloud cover? The last time we had that happen was in 2004, we lost 100 LMB, 200 BG, 3 CC, and 5 GC in a DO sag that was localized in the weedy shallow end of our pond.

Shorty is correct. Do sags or a localized loss of DO enough to kill fish can occur in just certain areas of a pond. I too had a fish kill in one end of an elongated pond.

Hi Bill,
The questions are answered here. The Pond is not like some lakes it is in the back yard 17X10and 4foot deep in middle with shelving. The largest fish may be 8 or 9 years old. The ones dieing are the smaller 1 year or two year ones 4-5 inch and these are Gold Fish that were bought as Feeders. The ones dead are generally in the 6PM hour when I get home. Shade- the pond is substantially under a large tree so it is shaded some part of the day. No algea bloom as the filter and sterilizer takes care of that- the water is pretty much crystal clear except when the bottom is stired up- there are leaves and rock pushed in by raccoons over time at the bottom- I have to do a one armed push up to get the rocks out of the deep area. I do not use chemicals except the Chloramine,Chlorine nutralizer since the fish death and since adding much tap water. It rained last night.Aeration pump was not running 24 Hrs but is now more so.Temp is at 25 degrees C presently.

im south and west of you but i noticed that there has been a lot of rain lately around this area of northern IL how is your pond handleing the rain is it possible some sort of turn over happened or is it possible some type of farm chemical or weed chemical could have been washed in? That is odd that it is the younger fish

Hello Creek Master,
I was at the point that I had to test the water for Ammonia. I followed the instructions of the kit and waited the 15 minutes to compare to the chart. It seems that for whatever reason, the pond had an increase in ammonia from what I can tell at .1 ppm or maybe greater. I went to a pond specialist location and he agrees with the local pond guy that I empty,clean and start again with fresh ingredients and sold me the temporary pond container, and bacteria once the new pond gets put back together. I have treated the old water with Amquel plus so as to allow the fish to survive till tomorrow morning when they will be transferred to the temp container and then the work will begin. He also confirmed that the 5 or 6 inch younger fish are more at risk than the larger ones- six more gone today.I just wish I had a handle on this much sooner. No, there was not that much rain to quench the run off in my yard and introduce fertilizer or other stuff into the pond.
I will let you good folks know how a make out and I will double my effort to be able to test water quality often plus probably add a water fall.

To all that helped out. I consulted a few experts- or at least people in the business around here. The suggestion was to empty the pond clean it and re-establish. After 12 hours at hard labor on Saturday it was clean.In cleaning the deep center area I found a fish under a rock that was dead for some time- plus all the junk and leaves. I now have a large gravel bet about 4" bottom and have put the fish back in but this time we counted the amount-it turns out we still have 178 fish. I would have never guessed that amount. We have added the Bio Boost to get things going but the store told me not to use anything else-on the container, it says to remove all chlorine from water. Will I have to start again with bacteria or should I put some clorine, chloramine remover in now.

Skywave-

Chlorine is very unstable. It will dissapate from water within 24hours on its own. If you feel uncomfortable with that, I would suggest a chlorine remover like EcoStarter or Stress Coat.

How much water are we talking about? I would feel safe with your 2400 GPH pump that after 24 hours most of the Chlorine is removed.

Hi Cary,
I don't know the exact amount of water as I never gauged it. The Pond is 17 X 10 and 4 feet in the middle. I usually add water in the afternoon to cool the pond down or to make up for evaporation. Not only are there two above ground filters but there is also an in pond filter that goes through a sterilizer before dumping into the pond. The other two filter dump water back in via 1.5" PVC pipes about 6 to 8 inches above water surface. Actually my one concern is that there is a quiet place in the pond for fish to rest so that they are not always fighting a current. Oh, the pond guy in this area says to keep the sterilizer off for a month or two while the pond gets back to normal. Most of the fish seem to be loving it at this point. More water tests tonight.
Thanks for your reply!

Update- A couple of more fish dead today and last nights Ammonia test did not show 0 ppm but seemed closer to what it was before I tore the pond down with the old water. Can fish Ammonia up a 17X10x4 foot pond in just 24 hours or 36 hours? I have not been feeding them as much as I have been in the past but then there are 50 less. In seeing the Ammonia not being the least my test can display, I loaded some filter bags with Fluval Ammonia remover and some black carbon and placed them in or around the output of one of the filters last night. I also just got some bio media to put in one of the filters used for just mech filtering. It is being rinsed overnight- it smelled plasticy.
Any other suggestions welcome.

Skywave,

The amonia will build up quickly until the nitrosanoma and nitrobacter bacteria communities develop.

Amonia will be fisrt, it will drop, next watch the nitrates, then it will fall and finally the nitrates will raise a little but go back down as the bacteria communities grow. That is one reason for turning of the UV. You don't want to kill bacteria right now.

With this much filtration and adding more biomedia along with the NH3 removal chemical, I think you may loose a few more fish but it should stabilize quickly. I would reduce your feed to every 2 days.

Maximum gallons of pond would be 5,000. Shelving and internal structures take up volume and makes the pond closer to 4000 gal maximum and probably less.

You stated above: "but this time we counted the amount-it turns out we still have 178 fish.... but then there are 50 less". This calculates to now about 128 fish. If you have 4000 gal, each fish has 31 gallons of water. This is not alarming if the fish are small such as 2"-6", but if the fish are larger then it becomes a big concern. Example: 10 6" koi are the equivalent biomass (waste producers) as one 12" koi. One 20" koi is eqivalent to 5 12" koi. 100 1" fish are the biological equivalent of 1 6" koi or goldfish. Readers should get the idea. I think 128 fish larger than 6" with some being 12" or longer, is too crowded for a healthy fish enviornment unless you are providing intense aquaculture conditions. Aquaculture conditions require daily monitoring of vital chemistries and iintense mechanical and biological filtration.

Many backyard ornamental pond people have the "stamp collector" mentality when it comes to fish. This view holds that the value of the hobby is directly related to the number of fish owned rather than the quality of the aquatic habitat provided. How many dogs and cats do you have to own before you consider them worthwhile pets? Is 128 too many? High fish loads means high bacterial loads. High numbers of bacteria puts a greater burden on fish immune systems and this increases the chances of bacterial infections.

One water quality issue not previously discussed are DOCs - dissolved organic compounds - that are a host of carbon based substances that exist in pond water. The main ones of concern are those dissolved substances derived from metabolic and biological byproducts such as fats, proteins, amino acids and so on. These substances have an insidious impact on fish health and are linked to disease causing bacteria in pond water. Ornamental ponds with dense fish loads are notorious for having unusually high DOCs. Best way to reduce DOCs is maintain low fish loads and occassional water changes.

I think all your problems with fish deaths will relate back to too many fish for the water quality within the pond.

Most importantly when one is dealing with a backyard ornamental pond, it is not so much the number of fish per gallons but one has to carefully consider fish biomass per gallons. Can you provide an estimate to us of what sizes of fish make up the 128 remaining fish in your pond?
I suspect that your pond does not have enough plant life to properly biologically filter the water to maintain its quality. Each 12" fish (abt 12oz) should have 112 ounces (7 lbs) of living plants (emergent and or submerged) in the pond or in an external filter for proper biologicial filtration.

Lastly it is important to realize that as fish grow, one should not add fish but remove fish, from the ornmental pond to maintain proper fish load balance. Example, you might have 36 4" koi in a pond today. But when they reach 6", the pond is overloaded and 27 fish will have to go. This assumes that the pond is properly maintained and receiving adequate aeration, and mechanical, chemical and biological filtration. To determine the maximum safe fish load for a backyard pond divide the gallons by 100. The answer is the number of 12" koi the pond should support. Remember, when the fish grow, one 24" koi is equivalent to 12 12" koi. I have tables and charts that provide fish biomass equivalents.

One last thought, I think is was a mistake to put all your fish back into a newly cleaned pond. The entire old fish biomass will create way too much ammonia and other waste products for the cleaned ecological system and the biological filtration to "handle" or process and your water quality will suffer until the fish biomass is reduced to safe levels (deaths) and/or the biological filtration re-establishes itself to the point it can handle the fish bioload.

Thanks Bill, I printed it all out to study- I would like the chart you speak of. I may be in trouble like you say. The amount of fish put back in was at 178 that day we have lost a few in the few days of transit mostly 4-5 inch fish again so we may be down to near 170. The pond has an internal filter,two external filters and an additional 2400GPH pump going for additional aeration. Today after rinsing I added a 5 gal bucket of bio media to the mech only filter to allow it to have a large bio filter as well. These are called Bio Balls (1125ct) I got from Foster and Smith. What worries me more is the temperature is going higher these days as well.The new pond seems roomier and has plants in both ends and some added just today that are floaters. I will see if I can offload some of these fish to other well established ponds people have-not just mud buckets.A few fish may near 9" but most are in the 5" range. Now the UV sterilizer is off to allow bacteria to repopulate as needed.The Sechi disc in my pond would be seen all the time.

I will try to put together a chart here for estimating fish bioload in ornamental ponds. This word processor is not real user friendly when it comes to making tables from data.
1. Divide the pond gallons by 100. This is the fish load limit (measured in 12" fish).
2. In the table find the appropriate size of fish you have in the pond & note the corresponding equivalence #.
3. Multiply the fish load limit (step 1) by the equivalance number (step 2).

This is the approx number of fish of given size you can keep safely in the ornamental pond. So if your pond will hold 30 12" fish, then it will hold 270 6" fish (30x9). It is ALWAYS better to error on the side of too few fish, because the fish you have will hopefully grow if you do not kill them first. Fish that are not growing at a normal rate are probably under some sort of stress.

Fish Lenght Equivalent----Number of fish
(Inches fish Load)---------to one 12" fish
2-------------------------------90
4-------------------------------36
6--------------------------------9
8--------------------------------4
10-------------------------------2
12-------------------------------1
14-16----------------------------0.5
18-20----------------------------0.2

One 12" fish and two 6" fish do not represent the same bioload in a pond. NOTE - expect your pond water to become green right after the biological filter is cleaned. It is not because nitrifying bacteria were washed away, but because the heterotrophic bacteria populations were dislodged. Lots of rapidly reproducing heterotrophic bacteria have been shown in studies to consume lots of phosphorus; more phosphours than the phytoplankton (green water). Phosphorus "feeds" the green water. Ornamental ponds often get real clear when the biofilter becomes clogged. As the biofilters become clogged with heterotrphic bacteria and other organisms the water will tend to clear up as the highly efficient heterotrophic community consumes phosphorus. This is why it is very beneficial to oversize biofilters (2X-3X) so the filters allow for substantial organic clogging by heterotrophs yet still allowing adequate or good filter flow rates.

Anyone else think Dr. Perca's come up with a couple of archive-worthy posts here?

Done - put under Bill's fish kills archive.

Thanks to all for their helpful advice!
The pond is stabilized and all chemistry that I am prepared to measure is looking good. I just received the Pinpoint DO meter and am reading to make sure I do the tests right and then will know my DO value. Plants doing well, fish happy acting- no more deaths, and my only hard environmental concern would be temperature. The temp will at times get to 30 degrees C but not very often-I add cool water by hose when I see this. My next large project will be the gas heater for the winter- any good priced items you guys know about?