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Robyn's Pond Care Page

Last Updated: 5/7/14

Filtering - mechanical, biological, and chemical
Cleaning - filters, cleaning the bottom, and water changes
Daily Chores
Getting Rid of Bees, Hornets, or Wasps by the Pond
Power Outages
Surface Foam
Finding Leaks - leaks, reasons water levels may drop
Keeping Animals From Getting Sucked Into Pumps

Note 12/28/98: Information on algae, UV sterilizers, building tips, stocking, winterizing, and seasonal care have moved to other pages. Go to the main pond page to find your way to their new locations.

Plant care is at my Aquatic Plant Page and fish care is under the individual fish that are indexed on my Pond Index.

Check out oxygen and aeration in ponds on my water page.

Here are some of my lilies blooming on July 21, 1997. The two white ones are albata, the pink one is Fabiola, and the orange one at the top is a Comanche. The Albata put out the most weight of leaves, the Chromatella (out of sight) put out the most leaves (a smaller kind of lily), while the Comanche flowered the most. All flowered heavily except the Fabiola which only put out half a dozen flowers all season.


During late spring, early fall, and summer, I feed my pond fish twice a day with a variety of goldfish and koi flakes and pellets. During mid-spring and fall, I feed them once a day (in the morning or evening; it depends) with an easy to digest pellet and some flakes. Do not feed the fish over the winter. Spring and fall foods should be mostly plant in nature and high in carbohydrates such as wheat germ, Cheerios, peas, and vegetables. Summer foods should be high in protein such as insects and meats. Vitamin C is important for pond fish so be sure it is included with the food, especially in the spring. Usually, ponders say that once the water goes below 50 or 55 degrees F, you should stop feeding the fish. If you do not overstock the pond with fish and have plenty of plants, you need not feed at all. The fish can live off of insects, algae, and plants. Feeding them allows them to grow larger, have more surviving fry, and generally survive longer but it is not necessary. Most ponders do it as much to see and commune with the fish as to feed them.

Generally, feeding what the fish will eat in five minutes is good to start. The rule for goldfish is that they are always hungry. They can overfeed and develop bloat or bacterial infections. Goldfish and koi lack a true stomach. If it is too cold, food will just rot in their digestive system. Be sure to provide food that is bite size for each of the fish in the pond. For big fish, use big sticks. For tiny fish, go with small foods. Hard foods should be pre-soaked in water for a few minutes so that they do not expand inside the fish. Choose a feeding schedule to stick to so that you are not tempted to overfeed the pond fish.

When the temperature is between about 50 and 60 degrees F, feed a highly digestible food, low in protein and high in carbohydrates (in other words, grains and vegetables). Some pond keepers feed Cheerios cereal to their koi and large goldfish in the spring and fall. During the late spring, you can supplement the Vitamin C in the food of koi with quarters of grapefruit. I tried this but my two koi did not touch them while others report their koi LOVE grapefruit! In the warm days of summer, feed foods higher in protein like live, freeze dried, and frozen insects and worms. I use Pond Care brand pond foods which have a red summer pellet and a larger multi-colored (vegetable) spring and fall pellet. The nutrition of fish is very complex and best left to the experts who manufacture and critique fish foods.

Here are two web sites with some interesting information on feeding pond koi and goldfish.
Feeding Koi and Goldfish.
Koi articles - includes one on making medicated koi food.


Mechanical filtration

Mechanical filtration is the removal of suspended debris including leaves, dirt, large algae-like hair algae, pieces of plants, dead animals, etc. It can be accomplished by filter bags, floss, brushes, foam, strainers, vortex mixers, physical removal, vacuuming (see cleaning), and many other choices. I use floss around the intakes of my pumps. After biological filtration, this is the most important, especially if you would like to SEE the fish!

Biological filtration

Biological filtration is the most important filtration for your pond. It can be accomplished with lava rock, hair curlers, bioballs, brushes, springflo, and dozens of other commercially available products. Anything that provides surface area for bacteria to grow in an oxygen-rich environment will allow biological filtration to take place. While it will occur on all wet surfaces in the pond that have enough oxygen, such a colony could not support the large amounts of fish that most ponders desire. See my water chemistry page to learn about the basics of biological filtration and the nitrogen cycle. The information also applies to a pond but on a grander scale.

Chemical filtration

Chemical filtration is accomplished with carbon, zeolite, or other resins. These chemicals remove organic compounds, ammonia, etc. from the pond. A healthy pond does not need chemical filtration as natural processes and water changes should be adequate. However, if you treated the pond and want to remove the medication, the ammonia spikes unexpectedly, or the neighbors' pesticides ended up in your precious pond, chemical filtration may be needed in a hurry. Usually, mesh bags (or put it in panty hose, see the secrets of pantyhose at my Fish Care Page Too!) of carbon or zeolite can be added to most filters for such an emergency.



Pond filters are notorious for becoming very dirty. Any floss, pads, etc. will need to be squirted off or even changed weekly in the warm months. Biofiltering materials like lava rock, rocks, balls, etc. will need to be cleaned a few times a year. During the summer, I squirt off the bioballs in my 1800 gallon pond's filter about once a month. The floss over the submerged pump requires weekly cleaning in my pond. This floss can only be retrieved by getting into the pond since the builders of my pond had no clue how to make a pond right. It helps to maintain biological filtration if only some of the biofiltering materials are cleaned at any one time.

Many people say not to clean the filter because good bacteria will be removed. See what I have to say about that at the bottom of my July 2007 newsletter under pond tidbits.

Cleaning the bottom

Ponds under about 500 gallons, will probably need to be totally drained and cleaned every few years. I clean my 50 gallon completely twice a year. Larger ponds should be vacuumed or in some way cleaned of debris and dirt as often as the owner is willing to do it. I bought a vacuum driven by the water hose for cleaning my large pond. It works well and adds water to the pond while I am at it. I use a wet/dry shop vacuum for the smaller ponds.

Water changes

The more water that you can afford to change, the better. Change up to, but no more than, 30% of the water every one or two weeks. The larger the pond, the less you need to change. My 1800 gallon pond gets changed when it rains as dirty water runs out the overflow. I also top it off every few days in the summer and every few weeks during the rest of the year. Because I have a well that is going dry, I cannot afford to actually pump out and replace water in the pond. A water truck filled it initially. Those with better wells or city water could change water more often. If you add city water, be sure to either add dechlorinator, let the water sit (where?) before using, or only change a little bit of the water. If you change less than 20% and provide aeration, dechlorination is probably not needed. Take note that some water sources are high in nitrates or phosphates and can actually result in seemingly dirtier water due to the resulting algae bloom. Water changes are really up to the owner. Rain, while it does change the water, can also yield algae blooms if dirt, debris, or polluted rain enters the pond. Dirt washes into my pond when it rains.

Daily Chores

1. Feed the fish when water temperatures are between 55 and 85 degrees F.
2. Add water to the pond if the water level is low.
3. Check around the pond for anything amiss including leaks, overturned pots, or anything out of place.
4. Check the pond for any sick, injured, or dead fish, frogs, or other animals.
5. Remove any floating debris or excessive debris such as leaves after a storm or in the fall.
6. Backflush or service any filters that need daily tending.

Getting Rid of Bees, Hornets, or Wasps by the Pond

This section has moved to this page.

Power Outages

Concerns when the power goes out

1. The fish will suffer a dangerous drop in oxygen levels and/or increase in carbon dioxide levels. This is usually not serious except in summer and winter. In summer, if the pond is warm and has a lot of fish, the oxygen levels can drop. In the winter, if the pond freezes solid (without the de-icer, bubbler, and/or waterfall), there will be no gas exchange. See my winterizing page for information on keeping a hole in the ice when you do have power.

2. The ammonia and maybe nitrite will increase to dangerous levels without filtration. This can be a real problem in ponds with lots of fish. In ponds with few fish, there should be enough bacteria on things in the pond to keep the levels low.

3. The bacteria in the biological filter will die. Bacteria start to die right away without food, air, and/or water. They cannot survive being completely dried out for long. In a pond, there should be bacteria on all surfaces to re-seed the biological filter when power returns.

4. When the filter is turned back on, dead bacteria and hydrogen sulfide, which smells like rotten eggs, will be released into the pond and harm the fish.

5. If they would normally operate during the winter, the filter, pipes, and/or pump can freeze up if it is below freezing or seize when power returns.

What to do while the power is out

(#) refers to which of the above concerns is addressed.

1. (1) Buy a battery operated air pump to keep the pond aerated.
2. (1, 2, 3, 4, 5) If you can afford it, you can buy any number of generators to maintain power to the pond. They also now sell solar-operated pumps (see OASE's solar page but they are even more expensive than a generator) which are a good option if you have a spare $1000+.
3. (2) If you have city water, water can be replaced or added to dilute the ammonia and/or nitrite and to increase the temperature in winter or decrease it in summer.
4. (1) If you have well water (turned off when the power is off) and a propane stove (that works when the power is out), you can boil some water in winter. Pour this over the ice to open up a hole or put the hot pot on the ice (be sure to catch it before it melts through!). Never break the ice with a hammer as the shock waves can harm fish. You can use your boot to pop a hole in the ice if it is not too thick.
5. (2) DO NOT FEED THE FISH. No matter what the temperature or how hungry they look, do not feed the fish! If fish eat, they will excrete waste which will raise the ammonia in the pond. Without a filter, this could rise to lethal levels. If it is too cold and the fish eat, the food could ferment in their digestive tract and kill them. Usually most fish will not want to eat if they are cold and in the dark. If you feed fish and they do not eat it, then the decomposing food can pollute the water to dangerous levels as well. In the summer, the fish may want to eat but do not give in. Most pond fish in bare ponds can go at least a week without any food. In well planted ponds with wildlife, most fish can go indefinitely without fish food being added.
6. (3, 4) Pour pond water over the biological filter material once every hour or two to keep the bacteria from drying out if that portion of the filter is not submerged. This also feeds ammonia to the bacteria. Without pond water moving over the biological filter, bacteria begin to die immediately. After a day or two, most bacteria may be dead. You can also put your biological filter completely in the pond to keep it wet.
7. (4) If the power is out for more than a day in warm months, unplug the filter system. When power returns, the first water out of the system can thus be diverted from the pond.
8. (5) Only when the temperature is below freezing in winter, unplug everything but the de-icer. That way, when power returns, the pond will begin to melt right away but the pump and filter will not seize up from ice blockage when power returns. If the system allows it, drain all the water out of all pipes, filters, etc.
9. (1) Add Microbe-Lift Ox which releases oxygen into the water if the oxygen levels go too low due to overcrowding without the filtration and aeration. A search on the internet will yield many places selling it. I do not know if this product just has hydrogen peroxide (H2O2) or another chemical. The addition of hydrogen peroxide will increase oxygen levels (and kill algae) but too much is deadly so it is risky and not advised. I do not know the proper dosage.

What to do when power returns if it is out more than a day

Note that if the power is out for less than a day that nothing really needs to be done.
If it is off more than a day, the pond's pollutants must be diluted, and the pond may have to go through the nitrogen cycle again. Even with days without power, the filter should retain some bacteria to restart the colony as well as all submerged pond surfaces. See the nitrogen cycle section for more information.

(#) refers to which of the above concerns is addressed.

1. (3, 4) Clean and/or change all the non-biological filter materials in the summer unless you changed them right before the power went out. There will be debris in them which may have grown fungus or bad bacteria. Clean filter materials will decrease the time it takes the pond to return to normal. Do not do anything to the biological portions of the filter.
2. (3, 4) Do a small water change during warm months. This will dilute the wastes left by the fish during the outage. Also, remove any dead animals.
3. (3) Add some liquid or powder concentrated bacteria like pond Stress-Zyme.
4. (4) In warm months, turn the filter system back on, and divert the first water coming out of the filter out of the pond until the smell is gone if present at all.
5. (5) Only when it is below freezing, turn any waterfalls, pumps, filters, etc. that would normally be going back on only once the pond is melted in those areas.

For information on what to do with an aquarium during and after a power outage, go here.

Surface Foam

Pond keepers often wonder about foam that can show up on the surface of ponds, often on hot days. This foam is the result of dissolved organic compounds (or DOC which stands for dissolved organic carbon) coming out of the water and creating foam. Moving water and aeration causes the DOC's to separate or fractionate from the water. There is a device called a foam fractionator that separates DOC's from water on purpose. Then, the foam is collected and discarded. Foam fractionators and protein skimmers, which are basically the same, are usually used in marine aquariums but can also be used in freshwater aquariums and ponds if desired.

On warm days, foam may froth at the base of waterfalls and fountains. This is especially common if the fish are ill or fish or amphibians have been spawning in the water. If there is a lot of foam, the foam should be removed if possible by dipping in a cloth or bucket to collect it. The DOC's come from multiple sources including, but not limited to, fish slime (which is produced in larger quantities if the fish have parasites, infections, viruses, injuries, etc.), sperm (and semen and eggs) [from spawning fish, toads (see here), frogs, etc.; very common], excess food (which is full of oily substances), rotting vegetation, and fish waste itself. My brother wants me to add humans (that would be me) in the pond (which are full of oily substances).

Doing water changes can reduce the DOC's concentration. Also, adding bags of fresh carbon will absorb some of the DOC's as well. In most cases, the concentrations of DOC's are low enough to not cause any threat to the animals in the pond. DOC's reduce the dissolved oxygen levels in water. In higher levels with lots of foam, the fish may have trouble breathing or otherwise show signs of stress. Foam can also occur in aquariums. It is usually a sign of stressed fish, spawning, or overfeeding, just as with ponds.

Finding Leaks

It is a recurring nightmare of many ponders, including myself, to go outside and discover the pond is low or empty. It is important to find out the source of the water loss quickly and efficiently. If there is still enough water in the pond that the fish are not in immediate danger, do not panic. First, turn off all electrical equipment, certainly if it is running dry. Then, look around the pond for any obvious problem such as a flooded area next to the pond.

If the water level has not dropped drastically, there are a number of steps to determining the source of a leak. First, with the pumps, waterfalls, fountains, etc. off, see if the water level continues to drop or not. This may take many hours to see if this is the source of the problem. Waterfalls and fountains can spit water outside of the pond if everything is not situated properly. If the leak is small and cannot be found right away, let the water lower over a few hours to a level where it stops going down. That means that the hole is at that level. By looking around the edge at that level, it may be possible to find the hole. The addition of milk drops around the edge may help to locate the hole. Where the hole is at, the milk will move towards it. Elsewhere, the milk will just dilute equally in all directions. You can also use food colorings instead of milk.

I thought I had a hole once and tried using the milk. The water level in my 153 gallon pond went down about four inches two days in a row. I figured it had to be a hole but it turns out that the deer were just extra thirsty on those two days! They have not done that since then. My ponds also can lose a lot of water on hot, dry days. Keep in mind that ponds can lose one or two inches a day when it is over 85 degrees F. Do not assume water loss is due to a hole in the pond liner.

If the water level is too low for the fish and no immediate remedy can be had, the fish must be quickly netted into holding containers. Most any plastic or glass container that has not had toxins in it will do in an emergency. It helps to keep a few clean plastic tubs around for this reason. They also work well for quarantining. Add as much of the pond water as possible to the holding containers and put in aquarium air stones if you can.

Once a hole is located, the water can be lowered to that level and a patch applied. Most water garden suppliers sell patch kits. If the hole is in the bottom, the entire pond will have to be drained. There may be a few patches that can set under water but most require the area to be dried thoroughly before application.

Reasons Water Levels May Drop:

Here is a link on finding a pond leak:
How to Find a Pond Leak!

Keeping Animals from Getting Sucked Into Pumps

I have various mentions of the pre-filters around my pumps on various spots on my web site so I thought I would bring them all together here (or at least link to those sections).

There are two keys to keeping small fish, tadpoles, frogs, insects, etc. from being sucked into or injured by a pump or its intake. First is exclusion. If they cannot get in, they cannot get hurt. Second is the dissipation of the suction power over as large a surface area as possible. Many pumps are sold with various intakes or pre-filters that can be added. Oftentimes, they may work just fine and are recommended. However, almost as often, such systems clog frequently enough to cause almost daily cleaning or impede the flow noticeably. For that reason, I set my pumps in to holed pond plant baskets and surround them with filter floss I bought from Aquamart, now AAA Pond Supply (see their filter materials section; they no longer sell the exact products that I used to buy). For the smaller pumps, then I put the whole thing into zippered nylon laundry bags sold by many grocery and general stores. These systems not only restrict animals from getting in there but dissipate the suction over a large area. During growing season, I squirt the floss, etc. once a week. The rest of the year, I do it twice a week.

If you have a skimmer, it is harder to keep animals from getting sucked in. I have never had one and cannot offer firsthand advice. Just be sure to have some sort of pre-filter. At least it can be cleaned from land unlike mine which require me to get into the pond.

Here are sections I have found on my site about my pre-filter systems:

My pump systems descriptions
Keeping animals out of intakes - see the tidbits section

Pet Link Banner Exchange:

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