How can anything decay in such cold water and create a build up of unwanted gases if closed off? Why do we have to worry about keeping it open? What is the science to this? And when lakes are completely frozen over why doesn't that kill fish?
How can anything decay and have a build up of unwanted gases with water so cold?
- Thread starter Donna Saverino MI
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The gases come from both the decay of organic material (which happens in the cold, albeit much slower) as well as from the fish respiration and excrement. Keeping an opening in the ice allows for both the gases that are building up to escape and oxygen to enter the system. In very large bodies of water the same thing occurs, but the volume of water is so much greater that the gas build up would take much longer to have the same effect as it would in a small manmade pond. The bio-load in a garden pond is far greater than any natural body of water.
So how long would it take, if ice where to form, to harm fish? You think hours, days, weeks? I'm just like to learn stuff.
Like on a garden pond? Lots of variables to consider - size of pond and number and size of fish being two, as well as how much organic material is in the pond. I would venture a guess that it would take more than a few hours and less than a few weeks - how's that for specific? haha!
We had one old time pond guy tell us that having rocks and plants around the edge of your pond means it's never completely sealed off - that gases will escape through the tiny gaps that those objects would create in the pond edge. But I have to believe the obsession with keeping a hole in the ice comes from real experiences people have had, not just fear that it MIGHT happen. So who knows... every pond is so different. I guess my motto would be better safe than sorry!
We had one old time pond guy tell us that having rocks and plants around the edge of your pond means it's never completely sealed off - that gases will escape through the tiny gaps that those objects would create in the pond edge. But I have to believe the obsession with keeping a hole in the ice comes from real experiences people have had, not just fear that it MIGHT happen. So who knows... every pond is so different. I guess my motto would be better safe than sorry!
Hmm... we have rocks and plants around the edge of the pond but the water freezes solid around them without any gaps that I've ever noticed. I'll stick to the de-icer too. 
Usually our pond completely ices over at least once each winter if we either forget to plug in the de-icer after a sharp temperature drop or if the de-icer fails. I would say the longest it's gone iced over was 24 hours at most. The quickest fix is to melt a hole in the ice with a boiling pot of water as we work on the rest of the problem. The fish have always survived. They are hardier than we give them credit for sometimes.
Usually our pond completely ices over at least once each winter if we either forget to plug in the de-icer after a sharp temperature drop or if the de-icer fails. I would say the longest it's gone iced over was 24 hours at most. The quickest fix is to melt a hole in the ice with a boiling pot of water as we work on the rest of the problem. The fish have always survived. They are hardier than we give them credit for sometimes.
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as Lisa noted, the ratio of fish load to volume/surface area is a lot different between lakes and our garden ponds. In fact, there ARE fish kills when the ice+snow exists for prolonged periods of time. I have a 2 acre natural pond at the end of my road and three years ago when we had a long winter and the temps in Feb reached record lows that did not relent until March, had one of these. The fish floated toward the shore and most were large. Between the lack of oxygenation and the toxic gas buildup, some can't survive. If you google fish kills in Michigan, you'll find reports of it happening even in larger lakes. But it takes the right conditions even then. IMO we depend on the typical January thaw to open up the waterways to allow this gas-off and re-oxygenation.
In our garden ponds, we're just guarding against the odds because our fish load to volume/surface area is a lot higher than the natural lakes. It doesn't take much to keep the hole open, so why not? And the best defense against winter is a deep pond with ample surface area. The smaller the pond, the more likely issues will arise. I have one client of mine with a 300 gallon preformed, probably doesn't go deeper than 18" and his gf seem to survive every winter. Gf are tough, more so than koi which are also pretty tough.
And as Lisa also noted, the decay process continues as there are bacteria which can survive colder temps. The activity is less but still on-going. This process uses up oxygen too, that's why having a healthy biofilm made up of algae is important because it too will keep putting out oxygen as photosynthesis continues. Of course this needs light to actually penetrate the ice, hence why fish farmers tend to recommend removing some of the snow on top the ice. I think once the ice reaches 5", the light is diminished too much, so it helps to keep the snow off as well. That said, I haven't done this yet and my fish seem to make it alright. I have lost one or two in various years and I put it down to a weaker fish/variety. I started using an aerator to keep the hole open then switched to a pond breather as it is a more secure system, imo. Easy too.
I suspect Lisa is having success with her system because the underground water tank is probably a lot warmer than her pond water would be if without. The earth's temp increases as you go deeper and if I remember correctly, tends to stay about 50 F down below the frost line. This means any pond that is dug in will get the benefit of this heat. Lisa's tank is getting that. I'm not a big proponent of keeping the water moving as I don't see any benefit, though her plant situation likes it better. For me, the risk of the pump and or system getting a leak or ice dam/bridge and emptying the pond is too high for little benefit. I do think the water is warmer at the bottom, even if only by a few degrees and I don't like mixing the top and bottom. I have a suspicion that if Lisa took the temp of her water, she'd find it is above what one would expect and that surely helps. Again, pond/lake fish are adapted to surviving this and as long as we guard against catastrophe due to our overloading of our ponds, the hobby has a great return!
Michael
Once the pond is sealed, frozen over, there is nowhere for the toxic hydrogen sulphide to go, the chemical reaction of stuff rotting continues to crank up the pollution, which normally gases off at the surface.
It does not take much for every critter that has gills, or absorbs oxygen through their skin, to die. Can be as quick as a couple of days if there is a lot of stuff going off.
An old rule of thumb is to melt a pan of hot water through the ice every other day, to relieve the yucky stuff
Native ponds have more ratio of volume to fish ratio, in flows and outflows, plant stems like cat tails acting like straws, reducing the hazard
It does not take much for every critter that has gills, or absorbs oxygen through their skin, to die. Can be as quick as a couple of days if there is a lot of stuff going off.
An old rule of thumb is to melt a pan of hot water through the ice every other day, to relieve the yucky stuff
Native ponds have more ratio of volume to fish ratio, in flows and outflows, plant stems like cat tails acting like straws, reducing the hazard
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I suspect our fish can survive a long time in a completely iced over pond, and most of the excitement is so the "experts" can feel important. Having said that, our fish are expensive and we have an emotional attachment to them, lets have some one else be the guinea pigs. I need to take a peek at my hole in the ice, it's been a couple weeks since i last checked.
It happens all the time. Winter fish kill off is very common in smaller mountain lakes, especially in colder climates.
I agree with that 100%. There's a definite point of no return... but finding out where that point tips is painful!
We have some small natural ponds in our neighborhood. They freeze solid every single year. Solid enough that the deer and other wildlife travel across them instead of around. No major fish deaths that we've ever witnessed. I often wonder what part the substrate plays in keeping a winter pond healthy, too. A rubber lined pond can't "breathe" or have any natural interaction from the bottom - what part might that play?
Lots of variables - we can learn from what we observe, as long as we aren't the blind men with the elephant!
Having witnessed many winter fish kills in local small lakes I don't agree with that at all.
If these lakes are supposed to be buffered from this threat by there volume, it stands to reason that our small backyard ponds would be that much more susceptible. Although I do wonder about the effectiveness of maintaining a small hole in the ice. Generally, when fisheries department takes measures to prevent winter fish kill in lakes they install large aerators in the lakes, they don't just try to keep a small hole open in the lake.
Of course, in warmer climates where the ice doesn't stay on the pond (or lake) very long, it is much less likely that the water will become oxygen depleted in the short time it is completely ice covered.
Well, perhaps the size of the opening is in direct relation to the amount of gasses you need to release. And the amount of gasses are in direct relation to the volume of water. A small hole in a large pond or small lake probably would be basically useless.
I think the general consensus is better safe than sorry. One never really knows at what point too much ice too long would be, well, too much! Why take the risk.
I think the general consensus is better safe than sorry. One never really knows at what point too much ice too long would be, well, too much! Why take the risk.
A vent hole for 20' of pond rings a very old bell here. Place an upturned plant pot over it and cover it with sacking, to keep the cold air away from the water surface in the hole...
The only way fish are going to survive a freeze over is if there is absolutely nothing decomposing in it, or a steady current of clean oxygenated water isflowing through
The only way fish are going to survive a freeze over is if there is absolutely nothing decomposing in it, or a steady current of clean oxygenated water isflowing through