Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Egg smell & water quality

Our pond has often had an eggs smell, when you would run an outboard motor, we now have an aeration system that often kicks up the same smell every now & then. Is it normal for a pond to have this happening? before a fishkill last winter, our fish were very healthy, huge bass & fat aggressive BG's.

Yes it's normal/natural H2S is produced in the decomposing prosess.
Standing water in well/tank/pit/pond............. can hold big amounts off most gasses.
Then when you stir it they are released, to air.

It is normally advised to start off an aeration system in an old pond slowly. Start with 1 hr. and add an hr. each day to slowly release the noxious gas. This could and will cause a fish kill.

I did follow this advise when I started the system for the first time. Just noticed from time to time an eggy smell.

The H2S is concentrated near the bottom including in the bottom muck as a by product of the decomposition and biological process.
When you start up bottom diffused aeration it stirs it all up and releases the gas to the surface. You can start the process slowly or not put the diffuser on the bottom to begin with and lower it as the water is turned over.

When a pond is drained for renovation. The egg smell is almost always there. Same is true when a valve is opened to drain off bottom water.

Moving the diffusers up & down after turnover is not an option. I guess every pond has some state of decomposition so an eggy gas would be present right? I have a nieghbor who is saying the egg smell means the water quality is bad, I was thinking it's natural because there is always a state of decomposition in the bottom of the pond, and the diffusers are doing good by releasing the gas so they dont build up. any input?

You got it right

Not after turnover as in thermocline but as in the water in the pond is circulated as in aeration. Common aeration produces complete pond water turnover from several times a day to several days. So you would start the diffusers at a shallow depth (5 feet) and lower the depth over a couple weeks to the bottom. Once there they stay there until you stop the system.

If you don't want to gradually lower the diffusers then you should use the slow start described by Burger above.

Thanks ewest for the information. Are saying if I would of started aeration as you suggest (shallow then move deeper) there would be no egg smell? I want to know if it's normal to smell egg as a process of aeration? Or in a healthy pond there is no smell? the smell (is from time to time)

I am not suggesting that method but simply pointing out there are 2 ways to start up aeration. Both are good for not mixing in to much H2S to quickly which is the goal. All ponds have H2S in some amount and it usually grows over time. A fully and properly aerated pond will reduce H2S over time as it is circulated to the surface and is dissipated to the air or broken down through chemical processes. The one thing you need to be careful about is circulating up to much H2S or low O2 water too quickly at start up by just putting the diffuser on bottom and running it 24/7.

I started the system slowly, so I don't think I am introducing too much at one time (H2S), our pond is 40 years old so i guess it will take time to reduce the H2S gas.