Pond Boss Forums AERATION Should I aerate? I Just Killed a bunch of Fish

I made an home aid aerator out of a Thomas air pump and some garden hose. I used a soaker hose approx 10 feet long that I weighted to sink to the bottom. (by the way a soaker hose makes millions of bubbles.) I turned on the system for about 15 minutes the first day. (Thursday July 3rd) Friday morning I got up at dawn and went to the pond to see hundreds of fish gulping at the surface. I then turned the system back on for about 30 mins. Friday evening I returned to the pond to find hundreds of dead fish floating. WHAT HAPPENED?

Let me set the stage.

30 year old pond
25 feet deep in the center
Approx 1 acre
100 deg F in the middle of the day
I have been feeding the fish for 2 years (fish chow)
Moss approx 15 feet out from the bank (all the way around)
3 feet below normal water level
15 Bass, 25 Cats, 100 Copper nosed BG (all dead)

Did I stir up the bottom that caused the water to turn? Did I release massive amount of methane gas from the bottom? Did I release oil from the decaying matter that coated the gill plates?

sorry to hear that. Makes me think twice about aerating my pond. I cant wait to hear the expert advice. This is relevant to my pond because it's about the same size and same age.

I assume you placed the air hose in fairly deep water.

One must be careful and patient when starting up an aeration system for the first time in a pond that has not been aerated for a while; this is especially true when aerating for the first time ever in an older pond. An old pond that has had decades to build up organic debris (leaves, pond plants, dead fish, uneaten fish feed, etc.) can have a large amount of anaerobic decay products built up in the bottom muck and in the lower water layers. Starting an aeration system too aggressively can pull this nasty decay products (including methane and hydrogen sulfide) up into the water where the fish are living with dire consequences.

It is also possible your air hose stirred up the bottom muck itself (which would probably been visible as dirty water), which may have released anaerobic decay by-products even faster than the above scenario.

In ponds like this (even in ponds beginning Spring aeration after taking the Winter off) aeration systems should be started up very slowly; just a few minutes per day, with very gradual increases in the length of time you aerate. The older and less aerated the pond has been, the more careful you should be.

I'm real sorry to hear about your fish kill that is a real shame. Once your fish began piping at the surface you were in trouble.

If you haven't already, I would read the entire Aeration section of the archives. There is some great information there. I will be eagerly awaiting a response from one of the aeration pros.

In addition to your questions, when a pro responds I think it would be helpful for us all to learn some of the following:

1. Given the scenario above, with fish piping at the surface on the morning of the second day, should aeration have been discontinued or was it too late already.

2. Could the use of soaker hose versus a set of diffusers had anything to do with this? My understanding is that in deeper water (25 foot deep pond in this case) you want to create a rising column of water. Did the type of diffusion have anything to do with this?

3. It seems like Pond Owner was being nice and conservative with a 15 minute start up, did the depth or age (or both) of the pond have anything to do with this rapid problem?

4. What should be done now? Should the water be tested for methane, hydrogen sulfide or anything else? Will these gases diffuse by themselves?

Once again Pond Owner I'm real sorry to hear about your situation, I think all of us feel a loss when a fellow pond meister has a fish kill.

I know what you mean Brett. Perhaps I'm just an overly cautious bean counter but when I'm ready to aerate I'm gonna have the system designed by one of our resident pros and I'm gonna purchase the equipment from them.

All you have to do is hear stories like this and just read the Aeration archive and threads and you will realize there is a lot more to Aeration than simply pumping bubbles into water. System sizing, diffuser selection, diffuser placement, water turnover rates are factors that need to be addressed by a professional (IMHO).

The things that Jeffhasapond previously mentioned plus numerous others should be considered or evaluated when doing aeration correctly.
AT LEAST several factors contributed to your fish kill. Some I my not address.
1. Soaker hose will move lots of water due to it producing very small bubbles; usually smaller bubbles than a membrane diffuser, often significantly smaller. Smaller bubbles more water than larger bubbles.
2. Stronger more powerful boil. Diffuser at 25 ft deep will create a very strong boil due to the further distance the bubbles have to travel to the surface compared to 10 or 15 ft.
3. With soaker hose laid directly on bottom, it re-suspended a fair amount of sedimented organics in the first period of operation. Suspended organics will contribute to and increase amount of biological oxygen demand above what pond normally experiences.
4. Summer water temps (80-90F) cause water to hold one half as much dissolved oxygen at 100% saturation as cool or cold water (39F).
5. ALL Water deeper than 6-8 ft in the pond at this time of yr probably had no DO. The DO that was there had been replaced by hydrogen sulfide (H2S) a highly poisonous gas to fish.
6. The volume of water in the deep unmixed zone of a deep pond is significant compared to that of a shallower pond of 10-14ft.
7. Moving a high volume of deoxygenated, poison laden hydrogen sulfide water the contained resuspended H2S sediments that increased oxygen demand in hot weather with maybe little sunny weather caused a large DO sag just before dark. In darkness the entire situation deterioriated and DO was dangerously low at daylight - morning - fish pipping.

8. Large amounts of Moss around edges enhanced the loss of DO at night since it uses oxygen at night vs producing DO during daylight.

9. Additional running of aerator the second day brought even more "bad" conditions and sediment laden water to the surface for twice as long as the first day. IMO that was enough to further degrade the upper water to DO below 4ppm to concentrations of 3 or less - levels that can kill fish esp when the H2S poison is also present. Strength or concentration of H2S in the unmixed zone plays a big role in this scenario
9. Diffusers on the bottom should ALWAYS be separated from the bottom sediments with either distance (on a stand) or a shield or bottom separator plate so the upwelling water is not in direct contact with the sediments so rising upwelling bubbles bring them to the surface. This rule is esp important during start-up aeration during early or mid-summer when increased H2S can make situations worse.
10 Normally one would not get into a fish kill with only running an aerator for 15 min the 1st day but certain conditions as noted above can COMBINE to make even 15 min of run time very risky and dangerous.

I hope your air compressor was not a rotary vane model. They are designed to only operate at a maximum of 18 ft deep. Operation at deeper depths shortens the life of the unit. Compressor for depths greater than 18 ft should be piston, rocking piston, or possibly, but not preferred, a diaphragm.

and THAT is why they call him the Pond Doctor.

Thank you Bill.

i do it the mother nature way
i have a windmill aerator, so it only makes bubbles when the wind blows , have the diffuser in 6-8 feet of water 4 feet off the bottom. diffuser located in smaller shallower area of 5 acre pond, have never had a kill pond is only 2 years old though

Thank You, Damn you guys are good! I've learned more about pond structure and aeration in the last six minutes than I had in the previous sixty years.

Pond Owner, I share your pain. I too inadvertantly killed a pond several years ago while treating plants. I would suggest you start planning and implementing the rebirth of your pond today. I found that bringing mine back lessend the pain of loosing it. Hang in there, good luck, and keep us posted. And by all means stay tuned to the expert advise found on this board.

Bill,
Is a soaker hose a good alternative to membranes (if used properly) since it seems to be more efficient?

Why is it that the cat fish were the first to show up at the surface? Thanks for all of the responces. I was (and still am) sick to my stomach. I have been doing nothing but reading all of the post on the forum. Bill you are correct. in the 15 mins that I had the air on the water went from clear to dirty. I sure thought that I was helping the fish.

It doesnt look like I have lost all the fish. There are still a bunch of CNBG and some LM bass fry swimming around the banks. This was the best year that I have had on the CNBG spawn. There were millions of small fish ALL over the place. Well i am just rambling.... Thanks Guys,,

P.S. is it safe to turn my feeder back on? Now that I have the kill out of the way..... Should I put the aerator back in the pond at an elevated distance from the bottom(say 10 feet)

Were the Cats the biggest fish? Usually in a low O2 kill bigger fish suffer first.

Some fish species are more tolerant of low O2 than others. IIRC, Channel Cats are somewhere in the middle of the susceptibility list.

Yea the cats were the first to go, a couple of the were 10 to 15 pounds. And the bass were about 5 to 8 lbs. and a lot of large CNBG.

Michael, Do you know the output of your pump,8- 10 ft of soaker hose could be like having 4-5 conventional diffusers.You are getting some great response to a serious situation.I would concentrate on known factors such as pump output and then match that to a diffuser and then be sure those two components match your pond size ,age, goals fish load etc,etc.Even sized properly startup in the summer can be delicate.It is almost impossibe without some system specs.Always have a footprint of some type under the membrane to keep the bottom sediments in place.

Ted, Here is all the info that I have on the pump

PULLS 27HG ON A VACUUM GAUGE AND PUTS OUT 35+ PSI COULD BE MORE IF YOU REMOVE THE PRESSURE RELEASE VALVE

It is a Thomas Vacuum piston pump. Suction on one side and discharge on the other.

Man it sure makes a lot of bubbles.....

Any model numbers,HP single or dual pistons? Should be something on it somewhere. Can you post a pic ??

Larger catfish may have been more vulnerable and stressed to the H2S gas than the low DO; both no doubt contributed.

Soaker hose is good at producing very small bubbles, but the tiny pores in the surface texture of the soaker hose have a strong tendency to become clogged and plugged much faster than a membrane diffuser. When cloged, soaker hose is quite a bit harder to clean than a membrane diffuser. NOTE: See Ted Lea's good comments below on this diffuser style about clogging of pores.

You ask: " is it safe to turn my feeder back on?" Do you mean fish feeder or aerator? Feeder can be on as long as fish will eat food. I would pul the diffuser and fix it so it does not pull sediments to the surface. Then replace it is shallower water so it does not bring more anoxic water to the surface. Gradually (maybe weekly) move diffuser to deeper water in 3 ft increments. OR just the rest of this year aerate water down to 16 or 18 ft deep. Then next early spring restart aerator in the deepest part of the pond. IN early spring almost all ponds are well mixed top to bottom and H2S is not present.

I will be at PBoss convention rest of this week.

I knew there had to be some drawback, or soaker hoses would be SOP with the Aeration folks.

One of several drawbacks to soaker hose and soaker hose style membranes such as MixAir is that when the pump is not running you now have water inside the diffuser even with a check valve. Planktonic algae,any suspended clay,calcium (if off for prolonged period) are now trapped. Standard manufacturer suggestion is to put additional cfm to it to clean (flex)but this does not work well in most cases.These products should be removed yearly and soaked in acid to clean (very outdated technology)the constant increased back pressure when monitored will tell you how fast you are plugging.Ill see if I can find some of my old pics of internal and external plugging and post later.It can be difficult enough to keep any surface clean let alone the inside too.

I use 3 of the round tree soaker hose scatered out in my pond. I run them 24 hours a day and do not seem to have any major problems. When you first start the aeration I ususally only run for a short time and try to build up gradually.

Here is a link off of ebay.

Ebay

You could easily power 2-3 diffusers with the 3.5 cfm that your pump produces at open flow.I would not suggest using 3 in your situation. Consider 2 units spaced apart with a regulator to slow the system to perhaps 2 cfm and still use a conservative startup.Having one central unit either on or off (all or none) is also risky.Regardless it will take "time" to slowly get your water where it is a higher quality for healthy fish but it will happen.

Is there a Book or a manuel that lets people know the exact amount of time to aerate when starting a new system? Is there a table or a chart that helps determine how long to aerate when starting for the first time or whether to start aerating at all?

The manufacturer should have that information for their particular system. Vertex Systems for example use a very conservative startup of 15 minutes initially and doubling the run time each day so that on day 8 you are 24/7 >>>>>15 min 30 min 1 hr 2hr 4hr etc etc.I have even seen this too aggressive in some older nutrient rich ponds.

My pond got the rotten egg smell after just a few minutes of running the blower. The pond had just filled up in June, and the pond had just been dug the previous Sept. It was an empty pond, nothing but dirt! I dont know what made the gas, but it sure happened fast. Since I didnt have anything in it yet, I just let it run and it has been running ever since. I have a single column of bubbles coming up from 17 feet down. Bobbi