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Re: how to prepare for winter 1000 lt pond

Subject: Re: how to prepare for winter 1000 lt pond
by Waterbug on 17/9/2013 18:20:40

Hi waterwoman.

I don't know where you live, climate would really affect the best options. So I'll just say some general things.

Yes, 10C (50F) is a good guideline to stop feeding. But it's not digital meaning 9C is certain death and 11C is perfectly fine. It's just a guideline people kind of all said if we have to pick a number, 10C seems reasonable.

As water gets colder the fish's systems slow down and they don't digest food as fast. The thinking is if we feed them a lot of food they could end up with a gut full of food which can cause problems. Just like some people have digestive problems and have to not eat too much, and/or too much of certain foods.

There are easier to digest foods (wheat germ based) that can be fed down to say 4.5C (40F). But most people don't bother, fish are OK without it.

If the water warms up (not the air) the question to ask yourself is what do you think the water temp will be over the next few days (including night lows). If it's spring you might start feeding when the water temp is 5C because you expect water temps to rise. Or you might play it safer and wait.

I don't go too much by water temp. If fish are active, seem to be looking for food, I might give them some, but in winter I won't give a lot. My thinking is there is food in the pond...algae, bugs, so fish do eat. I assume, like us, if they already have food in their gut they wouldn't eat more. Never believed Goldfish eat until they pop. However, I've been around pond fish a long time. I started slow, fed a little, see what happens. Next year a little more. And I do it only because I like too, not because I think the fish need it.

So the standard line, and I think it's reasonable, is to stop feeding at 10C (50F).

Whether to turn the pump off or on is a personal choice that should be influenced by climate.

In really cold climates there isn't a really good choice. The negative is when ice covers a pond gas exchange slows down (basically stops) and O2 drops and harmful gases increase. Fish load and the amount of decay determines the risk. I'd say for most ponds maybe ice covered for more than a month starts to be a concern. But it's not like a day or a week is a problem. Running a pump can keep at lease some hole for gas exchange in the ice unless the air drops too much for too long.

The plus side to ice covered pond is that it can keep fish warmer. Most people know warm water rises, but that's not entirely true. Water at 4C (39F) is most dense and will sink while water 3,2,1C will rise. Without any mixing from wind or pumps the water at the bottom of an ice covered pond can be 4C. Wind and pumps mix the water, allowing it to cool below 4C so fish can be in 0C water (even minus) water for long periods. Goldfish and Koi can survive much longer in 4C than 0C.

So the unfortunate choice is trying to figure out which is the biggest risk. Things to consider...Cold water holds more O2. Cleaning a pond before winter reduces decaying matter which would reduce harmful gases reducing the risk of ice covered for long periods. Fish load must be considered.

My own opinion is if you live in a climate where it is so cold that a pond is ice covered for more than a month a pump really isn't any kind of fix because it probably isn't going to keep a hole in the ice for very long any ways. So you end up with really cold water (although the ground will heat it back up) and poor gas exchange. Covering a pond is really what people in that boat use. Works great as long as it's not a floating type cover. You want air space between water and cover.

In moderate climates I don't think there's any great danger from leaving the pump on or off. Iced over pond for a few days, a week or two, is no big deal except for the very few people who have really big fish loads. In those climates even with the pump on water probably won't go below 4C (39F) anyways, and even if it does for a night or two the fish can normally handle that unless they're already in bad shape.