Heating Ponds in Winter. Never Use Gravel on Pond Bottom
Why you should not not use gravel on bottom of a pond
In any pond at any time there are a range of bacteria present. These bacteria are consuming waste products to survive. Some need oxygen to survive ... called aerobic bacteria and others do not. The latter are called anaerobic bacteria. In our pond we want lots of aerobic and preferably very few anaerobic ones since the latter tend to be involved with infections and unpleasant smelly situations.
If you have ever walked through the mud in a natural pond you will have noticed a sulphurous type smell and this would have been the result of anaerobic bacteria living in the mud (no oxygen there) and they metabolise using sulphur compounds amongst others.
It makes sense therefore to create garden ponds to avoid or at least limit the possibility of creating stagnant areas where these anaerobic bacteria can live and multiply.
Now consider a pond which has got gravel on bottom (like you would see in an aquarium) and ask yourself what happens to any food or fish excretions that settle down into the bottom of the pond ... yes of course they work their way down through the gravel where they build up in the absence of oxygen since no fresh water containing oxygen can reach these dead spots. These regions become breeding grounds for anaerobic bacteria. All sorts of problems can occur as a result.
In the early days of pond keeping gravel bottoms were popular because there was not a full understanding of what happens in ponds and the "technology" was based upon aquarium knowledge. The point about aquariums is that it is easy to vacuum the gravel using a minitiature vacuum pump ... in a pond this cannot be done.
In koi ponds great trouble is taken to ensure nothing stays on bottom of ponds through the use of bottom drains to minimize anaerobic bacteria possibilities. Removal of debris this way is for appearance reasons of course too. Because of the need to avoid anaerobic bacteria in pond water is a reason why sand filters are very bad for any type of pond ... dead anaerobic spots are inevitable in a sand filter.
If you already have gravel on your pond bottom then do yourself a favour and get rid of it before you create problems. The best time to do this now before water temperatures increase.( Southern hemisphere of course)
Gravel in ponds seems to be popular in USA as evidenced by a number of similar queries received while I was away. It really is not good for a pond to do this.
Getting ready for winter in cold areas consider a properly designed circulating water heater for larger ponds and a simple de-icer for smaller ponds
Seeing all those glaciers in Alaska and noticing a decided chill in the air I thought I would alert my Northern Hemisphere readers to some winter thinking about ponds. Thankfully here in South Africa we are enjoying the glorious early days of Spring.
If you have a largish pond and like to keep koi or goldfish and want to continue to see them grow through cold winter months then buying a special pond water heater is a real option since it will allow you to get water temperatures above say 50+ degrees at which fish can continue feeding. On the other hand if you are happy to let the fish "hibernate" in very cold water conditions then at least make sure you buy a low cost heater that will maintain a hole in the ice. This hole is required to allow noxious gasses that build up under water to escape and this will prevent fish suffering.
If you cannot afford a simple de-icer then boil a pan of water and place on ice surface ... this will thaw a hole and allow gases to escape. Do this periodically in areas where ponds freeze over for long periods. For me this would be a hassle especially sine the de-icers are low cost.
Proper Pond Heaters ...
Heating pond water requires water to be pumped through a heat exchanger that uses fuel of various sorts to be burned and in turn the burned fuel transfers its heat to the circulating water.
Typically these pond heaters are specified as follows ... and for each situation a recommended model will be given. It is also important to work on specified flow rates and rather than go into too much detail here since correct specification can be quite complex rather go to the site that sells them and makes enquiries there ... see link below table
| Pond Capacity gallons |
Required Boiler Output |
| 2000 | 16500 |
| 4000 | 33500 |
| 6000 | 50000 |
| 8000 | 66500 |
| 10000 | 83500 |
| 12000 | 110000 |
| 14000 | 116500 |
| 16000 | 133500 |
| 18000 | 150150 |
| 20000 | 166500 |
| 25000 | 208500 |
| 30000 | 250500 |
| 40000 | 333500 |
Click this link to go to site that offers many different heaters type heaters into search box that you will see and you will find a lot of information on installation and specifications. The information you will find will show you installation diagrams that will explain exactly what is required.
De-Icers for ponds (even patio and indoor ponds)
These of course are far more simple and low cost devices and can be viewed and explored at the same site ... ie click here . One of the models offered reads as follows and this will give you an idea as to how they work.
Heats the water, keeps open an ice-free area of approximately 30" in diameter at minus 40 degrees Fahrenheit. Thermostatically controlled, which shuts off at 60 degrees Fahrenheit. Heavy-duty float will not rust, corrode or leak. Special 10" heating element. 6' heavy duty grounded wire. If tank runs dry, heating element will not burn out. Individually packed. 120 AC voltage.
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