String Algae in your Fish Pond The Good, The Bad, and The Ugly



Consumes phosphates and nitrates – helps clean the water.

Source of food for your fish



Can plug up impellers in pumps



Simply does not look good. Visibility is limited.


OBJECTIVE:  Minimize the algae in your pond. The below product is available via Amazon.

ALGAEFIX  is approximately $40.00 per gallon. We have a 9000 gallon pond. When I see a lot of string algae growing, I will pour the recommended dosage into the waterfall. It will follow the water flow and circulate throughout the pond. Within a couple days, the majority of it is gone. You need to be CAREFUL not to use too much of this!. Use LESS than the recommended dosage, and monitor how it reacts to your pond. If you need to, you can reapply this every couple weeks, until it is gone. This product IS NOT harmful to your fish, unless you go beyond the recommended dosage. I have used it for several years, and it has managed the algae, and no fish have been lost. REMEMBER it is actually GOOD to have some string algae in your pond – it definitely does promote clean looking water!





If you have any questions, please let us know!














String al

Fish Ponds – Chlorine DANGER


If you are adding water to your pond, DO NOT use chemicals to control the chlorine. A GREAT alternative is to use a WATER FILTER. We have used this for several years – NO fish have been lost due to adding water. We normally replace the filter every 4-5 months.

See photos of the water filter. This is VERY EASY to use and INEXPENSIVE to buy.








Winter and your Pond


Here in the South Carolina Upstate area, we do get snow periodically, and the temperature does get below freezing.

Our pond has not been completely frozen over. With the moving water from the waterfalls (see photo above), it eliminates this.

We have a submerged pump that circulates the water. It stays on 24/7. Winter is no exception.

Fish tips:

  1. If you have fish in the pond, they will seek the deepest area of the pond. This is the warmest water. Your deep end should be minimum 2 feet – ideal is 3 to 4 feet.
  2. Koi are cold blooded. During the winter they slow down to a crawl. They are usually seen hovering in the deep parts.
  3. Koi should not be fed if water temperature is below 50 degrees. They can go through the entire winter without eating pellet food.
  4. If you have plants around the edges of the pond, the fish will eat that if the temperature warms up during the winter.








Designing Your Pond

View from lower pond

Once the location is determined, you need to decide on the size and design of your pond. Some costs to consider include liner, pump (should be appropriate size for water volume), cost per month to run the pump, cost of stone if you want a rock-lined pond, fish, plants, etc.

Design considerations should include different levels or depths if you want fish. The deeper area being should be 3 to 4 feet deep.  Be sure to plan room for plants for deep water, shallow water, moving water and edges (marginal).  Keep in mind that if you rock your pond (line with rocks) you will lose planting space and depth.  You will also want to design the outline or footprint of your pond with the size and cost of the pond liner as a consideration.  I recommend, however that you do not let the increased cost of purchasing more material hinder your imagination and creativity. If you can, you should go bigger that what you think you want.  You will be much more satisfied with your pond if you spend a little more upfront and fulfill your own creativity.  You will by this time know if you want a formal pond with straight edges, a round or oval pond finished uniformly with brick or stone or a natural looking pond with free formed curving edges of your own design.

We chose the latter for our pond – a “natural” looking rock lined, free form design, with non-uniform curving edges with consideration for the overall flow of water.  Our pond has many planting areas and 18 to 24 inch deep still water areas for water lilies.  The deepest part is about 4 feet deep so the fish have protection and places to overwinter.  We have a lot of shallow planting areas and a place about 12” to 15” deep for feeding and viewing the fish up close.

Here are some tips on designing your pond.


  • If you will want fish in this pond, you will want to have different levels or depths. We have it deeper in the middle and then it gradually gets shallower as it reaches the edge. The deeper level should be 3 to 4 feet deep. The fish need this depth for protection and to seek refuge during the winter. The edges should be shallow, so you can enjoy watching the fish close up. They also enjoy being fed in the shallower water.
  • We rented a mini excavator to dig the pond. My wife did the honors here. In our case, she used the backhoe to dig the hole for the upper pond, and then we manually used shovels to dig out the stream and lower pond. We made the hole for the upper pond deeper in the middle and then shallower on the sides.
  • Once the hole is dug, remove any roots or rocks. You do not want any obstacles poking holes in the liner.
  • Buying high quality liner is crucial. The last thing you want is for your pond to leak. Once the pond is full of water, finding a leak can be very difficult. I strongly recommend the Firestone 45mil EPDM liner. This is not cheap – but you should only have to order it once – it normally comes with a 20 year warranty. To get the correct footage for the liner, make sure you measure it correctly, accounting for the depth of the pond. I also recommend that you order extra liner, because you want extra liner around the edges. Finally, you will need to get underlayment. You will get this at the same time. Same measurements as the liner. The underlayment is to be put into the pond first, then the liner. Try to minimize the winkles in both the underlayment and liner. Any winkle in the liner has the capability to accumulate dirt and other materials.
  • 2011-274

As part of the pond design, (see photo below),   if you are going to have plants in the pond, you can put them in containers or you can do what we did. We wanted lilies, so we put dirt in trenches in certain locations in the pond, surrounded by rocks. (you can see two examples below). This dirt will not mix with the water. In the middle of the photo below we have positioned rocks to create a “fish cave”. We have several of these in the pond. The fish love these. Use different size and type of rocks to create what you want to see. We used 4 to 6 tons of different size rock to complete our pond. Rocks are not cheap. Scout around for places that will make deals and that will deliver to your house.

As you have the liner finished in the pond, the sides should have excess liner. Fold the excess up and put it under the rocks that you put around the edges. I would have at least a foot of excess. The remainder you can cut off.