Pond Boss Forums INTRO Questions & Observations Fish Kill

I am new to Pond Boss. A good friend gave us a subscription for Christmas. We have been enjoying the magazine. I hope that someone will be able to advise us as to a current problem we are experiencing.

We have a farm pond, about 1 to 1-1/4 acre, that I would guess has been there over fifty years. I am not sure of the exact depth but I would estimate it is about 10-12 feet at its deepest. It contains sunfish, bluegill, catfish, bass, and perch. Last December, we stocked some rainbow trout and have been enjoying catching them, both during ice fishing season this winter and so far this spring.

The past couple of years we have been experiencing more algae that we would like, and have recently installed an aeration system in hopes of controlling it. We also thought that this might help the trout during the warmer weather. The aerator has a dual output that consists of the air stone type delivery system that works from the bottom up.

The aeration system has been operatational for about three weeks now. Yesterday around noon we noticed a dead trout floating on the surface. By the end of the day we had removed a dozen trout, and five more so far today. I have also noticed that the water color is darker than before, and visibility is down (from about 18-20 inches to maybe 6-10 at most).

I am wondering if it is possible that the aeration system is turning over too much of the lower stratification, causing reduction in dissolved oxygen levels? We never considered this at the time of installing it, we thought that it would increase oxygen levels.

Sorry for the long post, but I thought it important to get in all these facts. Any suggestions or recommendations?

Welcome aboard, FPG.

There are two distinct possibilities. I don't know much about aeration, but I believe when you are first starting off with it, you only run it a few hours a day for probably the same issues you mention.

Also, warmer water temps may not allow the trout to survive through the summers.

Do you have a water temp that you can tell us?

You may want to shut the aereator off for now until things settle out.

Sorry, I don't have a water temp. However, the water did not feel warm yesterday when we were removing the dead trout, just the normal cool on top for this time of year and colder as you go deeper. I did ask my better half to turn off the aerator (as soon as he can get around to it) until we find out more as to what our problem is.

A hearty welcome to the PondBoss forum.

As your neighbor Sunil alluded, it may just be that the pond is warming too much for the trout. On Friday, my pond was about 78 degrees, 12 inches below the surface. The bottom cooler layers, even with the aeration, may not have enough oxygen for the trout.

I'm sure the great folks here will have a lot more answers.

Ken G.

Hopefully Ted and/or Carey or other experts from 'up yonder' will chime in.If properly sized, the aerator should have turned the pond over several times and oxygenated it by now.(May be latent low O2 death) If the visibility has been diminished, it may be that the stones are stirring up the sediment. Let us know how they are set up. They should be off the bottom, on platforms etc. to prevent stirring up the bottom sediments too much. It may be better in you part of the country for some stratification to occur to keep low temps. for the trout. Take temp readings at various depths and report. . Those are a lot of kinds of fish to deep happy, but should be able to be accomplished.

1.) Diffusion systems are not good aerators. Their main job is to destratify a pond by moving water using air, exposing it to air on the surface, but aeration is not as significant as an actual surface aerator. They are great for ponds and are very efficient at what they do, but they are not designed specifically for aeration. They will actually bring your entire water column to, or close to, late spring and summer surface temps, which is bad for trout once water temps reach 70 degrees. Optimum temps for trout are 55 to 65 F. Once your water column reaches 70 and keeps climbing you can kiss your trout goodbye shortly.

2.) Your trout would normally die this time of year regardless of whatever aeration you use, due to too high of water temps. Even surface aerators will, although producing oxygen, warm the water.

3.) If you did not mix you water column with the diffusers you could have bought a little time for your trout (cooler deeper water refuge), but your cooler water would eventually become too low in dissolved oxgyen especially in an old pond such as yours.

3.) Consider yout trout a bonus fish for fall, winter, and early spring unless you take measures to keep water temps low enough year around. This would most likely require aerated well water which can be expensive, and is required in copius amounts depending on the size of the pond. If you choose to do this, small is better, as it requires less well water. However your warm and cool water fish will suffer growth loss if you want them also.

And finally yes your diffusers most likely brought up some lower D.O. water, especially if you started up the system to late or didn't pulse it. The darker water may be due to an algae bloom crash, or your diffusers may be bringing up mucky sediment which in a pond as old as yours may also reduce D.O. Sometimes diffusers stir up the bottom at start up and sometimes they are installed incorrectly or maybe even upside down.

There are some of us here that grow trout out year around in ponds. But you will find our ponds receive well water or spring water, are fairly small, and if we use diffusers we only turn them on when air temps are lower then the optimum trout temps, such as at night. My trout pond is only about 90 by 45 feet and although only 8 feet deep it has very steep sides to keep warming down. I run about 41 gpms of aerated well water into the pond 24/7 from May to the end of October. Even then my surface temps will climb into the mid 60's when we have days when air temps climb in to the 90's. But once the sun gets low in the sky the temps start dropping again.

Well Cecil,

You explained it very well. The only success we have had is using a surface aerator at night with a draft tube at night only. This creates a "Cooling Tower" at night while producing oxygen at the surface. We have found that we can lower the surface temperatures down about 2-3 feet by 5-8 degrees.

Cary:

Is that basically using the aerator as an air lift to pull up bottom water?

Thanks to everyone for all your insight and advice.

We did not expect to be able to keep the trout all year. We know that they do not thrive in warmer water temps. We stock them occasionally just for fun, and this time it was one of my Christmas presents to my husband. Our pond is spring feed. Although I am not sure, I suspect that our pond is built at a spring site, as well as having more than one spring running into it. Even in the hotest part of the summer with drought conditions, our water level doesn't normally drop more than 6-8 inches and I can't recall it ever being more than a foot low in the past 17 years that we have had the pond. I was concerned because we have never lost this many trout all at once before. I was also worried about losing other species of fish as well if we did not determine the cause of the problem.

It appears that our diffusers were not installed properly. They are currently on the bottom. We will need to raise them up some. We have turned off the pump until we can remedy this situation. The instructions we were given with the aerator was to just throw the stones out into the pond. We actually stretched out the air lines (one is 75' the other 100') using our canoe and then dropped the diffuser stones in the pond.

Any advice as to how far off the bottom they should be?

It will be the weekend before I can take any temperature measurements. Our pond is on our farm in PA and we spend the weekends there, but during the week we live along the Potomac River in WV.

Thanks again!

I may get corrected for this but I don't see a problem with having them on the bottom as long as you have something under them. I fasten my diffusers to garbage can lids and if neccessary attach bricks to weight them down. I set mine by attached a long nylon rope and pulling them in postion with the air on to see where they are lcoated. Leaving the air on seems to keep them from flipping over too. Anybody else?

Sounds to me like you brought up some nasty oxygen robbing sediment by laying the stones in the muck.

As far as springs are concerned many don't realize ground water has little or no oxygen in it when if first comes out of the ground. Therefore just because you have springs on the bottom does not mean your trout will do well. The temps may be low enough, but may be quite anoxic -- at least at first. And depending on the how much spring flow, the cooler temps can be nullified by surrounding warmer water.