Transferred from. RE: got stock tank heater, help Posted by drh1 z4 VT (My Page) on Wed, Feb 21, 07 at 19:52 Air Exchange In Your Pond 101 Judging by several of the comments there is a bit of confusion on what is occurring with gas exchange into/out of your pond. I apologize for the length of this - feel free to not bother to read it (except for Rule #1). Rule # 1: If you have a pond and youve been doing something that works for you and youÂre happy with it....forget everything else and stick with it. Do not read any further. All other Rules: The following are "things" that influence the RATE at which a gas will go into or out of solution: a.) Water temperature - the colder the water the more of a gas can be held in solution... and therefore the higher the saturation concentration (commonly referred to as HenryÂs Law and is also dependent on the concentration of the gas in the atmosphere as well as the temperature); the colder temperatures will decrease .... somewhat.... the RATE at which a gas will diffuse through the water and into the air or from the air into the water. b.) Turbulence and mixing. The RATE at which a gas moves into or out of the water is controlled, in general, by a very thin film of water molecules right at the surface of the water (commonly referred to as FickÂs Single Film Model  as one example). The thicker this film the slower the RATE at which the gas can go into or out of solution. The more mixing or turbulence you provide the thinner the film. Therefore, if we arenÂt getting enough gas (oxygen, for example) into the pond we mix it, let it cascade down a waterfall, use a bubbler.. all of which cause the water to mix and "refresh" the surface and reducing that limiting liquid film thickness. The same applies to getting gases out of solution. c.) Surface area. Often people assume that this is the only variable or parameter that influences gas going into or coming out of solution. While it is a very significant factor it is not the only thing that is relevant. Obviously more surface area is better but there is a point of diminishing returns when there is so much surface area that there is little significant increase in the RATE of gas transport. When we use a stock tank heater or a pond heater the surface area is obviously the amount of clear water surface that we see. However, when using a bubbler the surface area is NOT the size of the hole from which the gas is exiting but rather the TOTAL surface area of each and every bubble that is produced under water. So if your bubbler is putting out 4 liters of air per minute, with an average bubble diameter of say an 1/8 inch you will be producing a little over 80 square feet of surface area each minute. The finer the bubble, the more the surface area. This is why bubblers are much more effective in promoting gas exchange than something that opens up a 2 foot or 3 foot hole in your ice (~9 - 27 square feet). So what size hole should one have? There is no specific answer for this nor can there really be one. It depends. If you have "a lot" of fish in your pond then youÂll need more surface area for gas exchange than if you have one comet in your 2000 gallon, lake. Secondly, water temperature also rears its ugly head again. As a general rule of thumb (which means itÂs not accurate at all!!) biological activity doubles for every 10 degree C change in water temperature. So if your pond is at 2 degrees C versus 12 degrees C then the amount of wastes produced and consumed will be significantly lower than for the higher temperature. This means that if you intend to keep your pond a nice, toasty 45F all winter with your pond heater, immersion heater, solar heater, backyard barbecue grill, etc. then youÂre going to need a significantly larger amount of surface area than the person that lets the pond sit close to freezing. The assumption that your fish huddle around your heater holding their fins out for the warmth is a bit too much anthropomorphizing! Being of New England stock and heritage means that my DNA is such that I donÂt like to part with my ÂLincolnsÂ... and I mean the one cent variety. ThatÂs why I use a bubbler here in zone 4. My pond is pretty close to 3000 gallons (as a guesstimate) with a depth of only 3 feet. IÂve had ice as thick as 18" on it (about 2 years ago if memory serves me correctly). Essentially all of my fish survive and appear to be well each spring. Sometimes there are a few less of the smaller comets but I happen to know for a fact that the Koi will munch on them over the winter. All of this with nothing more than a 4.5 watt aquarium air pump! My electric bill never sees the difference. The URL below should give you access to a pdf file that was mentioned by Horton...it describes what I use for a bubbler system. I would not recommend it for small ponds in zone 4. ThereÂs even more that we could discuss but IÂve obviously babbled on long enough. ÂDavid

I feel more confident now about putting a rubber liner in there if I need to. Good news is that my neighbor who has 20 fish is willing to give me 3 of them to try this afternoon. He says for the winter I could just dump them back into his pond. He's bringing me some food to get started with too. He doesnt know what kind of fish they are, he bought the house and the fish came along in the pond. I am going to try to ID them, maybe I could post a photo of them. We're thinking of fish names right now. I have the pump that makes the water go up the waterfall then trickle into the pond. I hope that's all the equipment I need and I hope that pump is sufficient to make oxygen, cuz I think they need that, not sure. Will I have to run it 24 hours a day?

Glenda! I miss chatting with you too, I emailed you, I guess you didn't get it? I need you to email me a photo of your patio lol! I'm not bothered about the work I did to the old house, the one I have now is way nicer and I didn't have to do anything to it. :D Thanks to everyone for the suggestions about the plants, I'll do that today. I was afraid if I did that, I would spur them into putting up new growth too late in the season and they would have a hard time going dormant (I'm a rose grower also LOL). I will do that today and hope for the best!

Some ponds are never cleaned and the ponds and its occupants survive very well. However, a large number of ponds are created with high fish densities or are built in locations were the pond receives a great deal of debris over the year. Even if you start out with just a few fish initially, in a healthy pond they will breed to the point that the number of fish will push the environmental limits of your pond and biofilter. The debris may be the result of leaves blowing into the pond, the die-back of vegetative pond plants as well as fish wastes. It is these latter types of conditions that will necessitate you cleaning the pond eventually. The two most likely time points for cleaning are in the fall, to reduce the amount of accumulated muck on the bottom of the pond as you head into winter, or in the spring to remove material accumulated over the winter from leaves blowing into the pond, accumulated fish waste or catkins and similar materials shed by trees as they leaf out. Cleaning in the fall reduces wastes in the bottom of the pond which may turn anaerobic if sufficient oxygen is not available, creating a breeding ground for harmful bacteria, or which may decompose, releasing ammonia and other dangerous chemicals that can be trapped under the ice. The build-up of these pollutants can lead to fish kills over the winter months. While keeping a hole in the ice over winter will help alleviate the accumulation of gases, cleaning the pond before winter sets in will reduce the overall potential for problems. Cleaning the pond in the spring may help reduce diseases and parasites that often occur as the pond and its biology warms up for the summer, as well as reduce the overall availability of nutrients that stimulate algae growth. The following are a few approaches that have been successfully used to clean the pond. 1. If the pond has a bottom drain periodic changes of water (typically 10% per week) have been used to evacuate the accumulated debris from the bottom of the pond. This simple approach minimizes the amount of material that is removed at any one time as well as adds water to the pond on a periodic basis. Care must be taken when adding water to be sure that you have minimized the addition of chlorine and chloramines typically present in many municipal water supplies. This can be done either by pre-treating the water with dechlorination agents or by using a whole-house water filter with an activated carbon cartridge. 2. Using a net such as used in swimming pools is helpful for cleaning out large materials that have settled to the bottom of the pond. However, if there is a very large amount of debris in the pond you should be careful to either remove the fish or use supplemental aeration to avoid creating significant oxygen deprivation due to stirring up anaerobic or large amounts of oxygen-consuming muck. If you notice a rotten egg smell this indicates the presence of hydrogen sulfide. You should immediately stop stirring up the bottom and get the fish out of the water as soon as possible before continuing with the cleaning. 3. You can use a variety of devices for vacuuming the bottom of the pond. Some of these use a garden hose to create a suction through a venturi device. The potential problem with these devices is that the pond may fill up with too much water during a prolonged vacuuming and you may have a potential problem of adding chlorine and chloramines to your pond if you do not pretreat the water. Wet/dry shop vacs, specially those with an attachment for a garden hose to provide a continuous drain, have also been used. These devices may drain a large amount of water from the pond in a short time and therefore it is necessary to either replace the water or use the garden hose to add the water back into the pond through the biofilter. Care must be exercised in reintroducing water taken from the bottom of the pond in that it may be depleted of oxygen as well as have very high suspended sediment levels that may create problems for the fish. A third approach is to use a pump capable of handling a moderate level of solids (such as a sump pump) to pull water from the bottom of the pond and pass it through a device to strain out the majority of the solids and then recirculate the water back into the pond. Filtering materials such as old sweaters, panty hose, etc. have all been used with some success in this approach. In any of these approaches, if using an electrically powered device running on house voltage make sure that you have it plugged into a GFI protected circuit for your own safety. Ronaye, Steve and David