Winter Air Stone Level

[MoonShadows]

I remember reading more than once here that you should raise your air stones up off the bottom during the winter, and if I am not mistaken, the recommended height was about 1 foot below the surface, but I can't remember the reason why, and can't find it now. Can anyone enlighten me? Thanks!

 

[brokensword]

I'm one of those that has often forwarded that info, MS. The reason being that when set low, you pull the warmer water from the bottom and mix it with colder water nearer the surface. The idea is to keep as much warmth as you can where the fish hang out. Or rather, they hang where the warmest water is, so why make it colder than it has to be? I got this info from perusing Lake-pond owners on a forum where some showed a greater fish kill happened when the aerators (only during the winter) were placed low in the water. And since you're not getting any real aeration from the bubbles, the only reason for the aerator in the winter is to keep a hole open in the ice. Hence, you have a better chance where the air has less resistance during the upflow. That said, if you don't have enough aeration at the surface in the winter, the ice can still form over it. Trust me, happened to me one time. 12-18" below the surface is what those on the lake-pond forum found was best.

In the summer, aeration is a different kind of animal...

 

[MoonShadows]

Thank you @brokensword. keeping the warmer water closer to where the fish are and increasing the ability for the aerator to keep a hole open makes a lot of sense. I just couldn't remember, and I thought it had something to do with the surface agitation, and in a way it does. It's the increased agitation that betters your chances for an opening.

 

[addy1]

A friend had a aerator in their pond one winter, not as cold as this one, but cold. They lost every fish in the pond. Too powerful, too much air movement chilled the water

I use only a pond breather since that happened. One year I used a small fountain pump, think 250 gph, with the output right below the water, it kept a nice tiny hole in the ice.

But pond breathers are so much easier, put them in forget about them. I do check that they are still running off and on

 

[MitchM]

My experience has been that any circulation whatsoever will equalize temperatures in the pond so I don't think it really matters where the air stone is located - and if your ice gets more than 1 foot thick (like mine) the air stone will wind up sitting in it's own little pool of well aerated water.

 

[Gemma]

I almost moved mine up this passed Fall, then I thought I never done it before and the fish have been fine so why chance it, and so I left it alone, close to the bottom where it always has been. It sure did a good job keeping the hole open in below zero temps

 

[RobAmy]

With my setup the stream turns over the water temp faster then the air pump for sure. My air stone is at a higher level by default due to the location of my skimmer. I leave the air pump running year round. My pond has been completely frozen over in years past like this year with no fish loss. Just the air hole is open. This is the air hole while the stream running also with ice covering the pond. Now just the air hole and no stream running.

 

[brokensword]

My experience has been that any circulation whatsoever will equalize temperatures in the pond so I don't think it really matters where the air stone is located - and if your ice gets more than 1 foot thick (like mine) the air stone will wind up sitting in it's own little pool of well aerated water.

From the research I did with people that raise fish for eating in ponds, having the airstones low was problematic at best and disastrous often. Since no aeration really takes place by putting the airstone low, what advantage is there? Certainly the circulation at the top won't mix with the lower layer, esp if the warmer water is at the bottom. If you had a pump, I can see the mixing but especially near the surface, I can't see much mixing at all. So, can't really ever recommend putting the airstone down low, especially after reading serious fish farmers having issues doing it that way.

Used to be a link to the forum/info that I posted here, but I'd have to search back quite a bit to find it.

Here's one I just found; will look for the original, more in-depth conversation;

https://www.bassresource.com/fish_biology/how-aeration-winter.html

and another; this is the same forum I first searched, though this may not be the exact conversation. Still, it's mirroring what I said.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=353617

another;

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=430506

This is the one I think I originally read;

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=429047

 

[MitchM]

From the research I did with people that raise fish for eating in ponds, having the airstones low was problematic at best and disastrous often. Since no aeration really takes place by putting the airstone low, what advantage is there? Certainly the circulation at the top won't mix with the lower layer, esp if the warmer water is at the bottom. If you had a pump, I can see the mixing but especially near the surface, I can't see much mixing at all. So, can't really ever recommend putting the airstone down low, especially after reading serious fish farmers having issues doing it that ways.

Used to be a link to the forum/info that I posted here, but I'd have to search back quite a bit to find it.

Here's one I just found; will look for the original, more in-depth conversation;

https://www.bassresource.com/fish_biology/how-aeration-winter.html

and another; this is the same forum I first searched, though this may not be the exact conversation. Still, it's mirroring what I said.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=353617

another;

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=430506

Stratification doesn't occur in our ponds that are 5 feet deep or less. If there is any difference, it's minimal.
I've had sensors at 2 foot and 5 foot levels and unless the water is absolutely still, the temperatures were identical. By minimal difference, I mean about 1 degree Celsius.

And no, bottom aeration doesn't provide aeration at the lower levels it only provides circulation.
Bringing colder water to the lower levels of a deeper lake would change the dynamics of the biological activity so I can see how that could produce negative results.

Our stocked lakes here use surface aerators to prevent winter fish kill, but again, they are much deeper than our garden ponds.

 

[brokensword]

Mitch, I don't believe my fish would hang out at the bottom if it wasn't appreciably warmer. The water has to be colder nearer the surface and why would I want to mix that colder water with the obviously warmer down below? I understand that you need 6+ feet and deeper for stratification but the fish aren't on the bottom for no reason...again, what benefit is it to have the aerator at the bottom? Ask addy about her friend that lost fish by having the aerator low in the pond. If the idea is to keep a hole open, how can it not be easier to do this when the bubbles are nearer the surface?

Again, no good reason NOT to have the aerator near the surface. That said, I'd still opt for a pond breather now and not even worry about this method.

 

[brokensword]

and another thread noting mixing of top and bottom layers of water...

http://www.koiphen.com/forums/archive/index.php/t-142565.html

 

[MitchM]

You can place the air stone wherever you like, what I'm saying is that in our shallow ponds, the water temperature will equalize given the slightest circulation. My own measurements back that up.
Choosing an arbitrary level of 1 foot deep doesn't reflect the varying thicknesses of ice that will occur.
Perhaps the only benefit by having the air stone higher is that water circulation is reduced at the lower levels.

Fish may be staying in lower parts of the pond simply because they don't have to expend as much energy during the winter fighting a water current or being disturbed from overhead activity that they can see.

Addy's neighbour's situation is troubling but we really don't know a lot of information either. Addy's neighbour's fish could have simply run out of stored fat to survive the winter.

As far as that other forum goes, I find people will "support" someone's advice based on who is providing the advice rather than the quality of the advice given. It makes it difficult to have a constructive discussion.

 

[brokensword]

You can place the air stone wherever you like, what I'm saying is that in our shallow ponds, the water temperature will equalize given the slightest circulation. My own measurements back that up.
Choosing an arbitrary level of 1 foot deep doesn't reflect the varying thicknesses of ice that will occur.
Perhaps the only benefit by having the air stone higher is that water circulation is reduced at the lower levels.

Fish may be staying in lower parts of the pond simply because they don't have to expend as much energy during the winter fighting a water current or being disturbed from overhead activity that they can see.

Addy's neighbour's situation is troubling but we really don't know a lot of information either. Addy's neighbour's fish could have simply run out of stored fat to survive the winter.

As far as that other forum goes, I find people will "support" someone's advice based on who is providing the advice rather than the quality of the advice given. It makes it difficult to have a constructive discussion.

I hear you re 'who is giving'; here is where we're really going to miss Meyer. That said, I doubt so many fish all 'ran out of stored fat' at the same time. So, not subscribing to that possibility. Since there is evidence fish can be lost when airstones are placed low, I'm going to lean on the side of caution and suggest a higher placement. These people too are basically testing ponds for the likes of us. And there's no way I'll believe the bottom of the pond is less than 2 deg difference from the top. Whatever the temp is though, the fish prefer this. My pond has no flow/movement so there's not going to be any mixing per se. The fish could hang in the middle if the temp was the same as the bottom and they're not.

I do think when you use a pump (keeping it going all winter) that you are essentially making the upper layer and the bottom layer the same. I'd rather keep some differential, no matter how small, in tact. Doesn't mean there's not benefits as I can see them based on others' experience but to my mind, it still raises the risk. If you read any of the links, you'll see that having clear ice is better than covered, that fish kills happen most often when both ice and snow coverage is prolonged. That fish are fine for many days (months) if there is enough depth and light can intrude. And I can say from my experience in my own region, that the years we don't have a typical 'January thaw' are the years you hear and see fish kills. Never in other years, not to my knowledge. So I don't worry unless the ice is prolonged and snow covered, AND there's no opening to allow for gas escape/oxygen transfer.

I tried looking for some data that is more 'small pond' oriented re ice temps but didn't find much. Mostly what I read was from University studies and fish farmers, who no doubt have more invested than most of us. Too, their setups were much (better) deeper but I bet their fish load is much more. And too many are suggesting keeping the aeration only for opening a hole (not oxygenation) for short periods of time. I'm inclined to lean with them as if their methods work better, I'd rather emulate than ignore.

It still comes down to 'what good comes of bottom aeration in winter?'. Until there's evidence to that fact, I'll still suggest upper level location. And if it doesn't make any difference (to you) per your findings, why not also err on the side of caution?

 

[MitchM]

I hear you re 'who is giving'; here is where we're really going to miss Meyer.

Agreed. However, there is a lot of data out there; Meyer sent me quite a bit off-line and I'm looking forward to see what he sent Ian.

...That said, I doubt so many fish all 'ran out of stored fat' at the same time. So, not subscribing to that possibility. ...

That's one area where we don't know what happened. The fish population could have died over an extended period of time and the bodies were only noticed after the ice cleared. We also don't know the strength of circulation pattern.

I... And there's no way I'll believe the bottom of the pond is less than 2 deg difference from the top..

Why would you not believe this when you have no data to back that belief up? You yourself said you know a pond needs 6+ feet for stratification to occur.

I'm leaning more towards the situation where fish will go to areas of least disturbance, which would be the lower areas, because ice will creak, crack and groan as it grows, shrinks and is moved by the wind. If the lower levels also have less circulation, even better. That's my opinion, anyways. I haven't found any data yet to back that up.

.

 

[brokensword]

Agreed. However, there is a lot of data out there; Meyer sent me quite a bit off-line and I'm looking forward to see what he sent Ian.

That's one area where we don't know what happened. The fish population could have died over an extended period of time and the bodies were only noticed after the ice cleared. We also don't know the strength of circulation pattern.

Why would you not believe this when you have no data to back that belief up? You yourself said you know a pond needs 6+ feet for stratification to occur.

I'm leaning more towards the situation where fish will go to areas of least disturbance, which would be the lower areas, because ice will creak, crack and groan as it grows, shrinks and is moved by the wind. If the lower levels also have less circulation, even better. That's my opinion, anyways. I haven't found any data yet to back that up.

.

My main 'data' to support the lower depths being warmer (still) is that the fish don't hang in the middle. Why choose the lower? There's no disturbance in my pond at any level, save for right next to the pond breather. If there was no actual advantage to being lower (and I don't mean 'on the bottom proper), then why do the fish go there (no disturbance, remember?). And if the earth is doing any heating at all, wouldn't it be 'warmest' on the bottom as it's furthest away from the ice and nearest to the 'warmth' of the earth?

It is hard to analyze what happened to addy's neighbor, but it's too coincidental that the fish all died at the same time and were healthy upon entering winter. If something (a toxic agent) didn't enter the water, I have to believe the fish were starved of something or succumbed to the conditions (here I'll call it super-cooled water). That said, I did pause as the story unfolded when I learned the temps fluctuated quickly in a short span. I think that might have had something to do with their demise but of course, have no evidence. I'm still skeptical that ALL the fish would be lost just because the aerator was low, but again, too coincidental for me to totally dismiss. If I hadn't read those forum posts re aerator placement and their findings, I'd not have thought much about where my aerator was placed either. Again, too coincidental to ignore. And in the face of 'little data' but anecdotal evidence, I lean toward erring on the side of caution. When the stories are confirmed (data acquired) of fish dying during the winter and ONLY an aerator (set nearer the surface of a proper depth pond) is used to keep a hole open, then I'll reconsider such a suggestion.