Algae Control FAQ

What causes algae to form in ponds?

Algae can be caused by de-oxygenated water, excess sunlight, fish being fed too much, high levels of organic waste in the water, but the two most common factors are too many fish being fed too often and lack of leaf control in the fall!

What is the best way to control algae in a backyard pond?

To put it simply, lower the nutrients in the pond. Have a large filter, apply beneficial bacteria regularly, and keep the fish population reasonable. Aquatic plants help as well because they consume some nutrients from the water that would otherwise feed the algae. The goal for a healthy and lovely water garden is to have green, fuzzy sides and bottom in your pond, with water clear enough to see to the bottom.

How many weeks should the pond be treated?

The goal is to get the algae under control initially by applying beneficial bacteria weekly. The product amount can be adjusted as the good bacteria colonizes and grows. Usually it takes a few months of regular applications though. Estimate anywhere from 8 to 20 weeks depending on the severity of the algae, the nutrient load, the water pH, rainfall, temperature, cloudy days and numerous other factors.

How do I get rid of algae?

Some algae is a normal and necessary part of your pond. Clear water with algae on the sides and bottom of the pond is a perfectly balanced pond. To get a balanced pond you need to have about 40-60% of your pond surface water covered with plants such as water lilies, hyacinths, and lettuce. Also, it is important to have a certain amount of oxygenating plants (such as anacharis or hornwort) on the bottom of your pond. This formula will help give you clear water. A healthy, balanced pond with the right amount of fish and plants should be free of "green water" at least 10 months of the year with no special care. Remember, some algae is a necessary part of a healthy pond’s eco-system.

What kinds of algae are there and how do I control them?

There are two basic types of algae that can occur in most ponds. Single cell algae which looks like pea soup and string algae (also called filamentous or hair). Single cell, free floating algae is the most common cause of green water in ponds. Your water garden may go through a “green pea soup” phase before your plants become well established. This is normal, harmless to fish and plants and should clear up as your plants grow and absorb the nutrients the algae needs to survive. DO NOT drain your garden and put in fresh water, it will just repeat the same green water phase until a balance is reached! Once balanced, your pond should remain clear enough to see the bottom of the water garden at least 10-11 months of the year. To speed clearing of the water, add more competition for the algae (more submerged and floating plants), reduce the number of fish (fish waste is a natural fertilizer for algae) and remove any plant and leaf debris that has collected in the pond. Limiting fish feeding to once or twice a week will also help since the fish will forage more thoroughly for other food sources that may otherwise add to the debris in your pond. Make sure any food that is not eaten in 5-10 minutes is removed. Weekly applications of beneficial bacteria such as Hydro-Bugs or Green-be-Gone can be very effective. String algae can be controlled with algaecides, phosphate removers or high tech equipment such as electronic clarifiers (ex: IonGen).

How do I control algae on my waterfall?

Growth of mossy or stringy algae on your waterfall can be minimized or eradicated by the application of products such as our Oxy-Pond Stream and Waterfall Cleaner which is fast acting, very effective and fish-safe. We use this product on our own display ponds!

Will snails help with algae?

Freshwater aquatic snails will eat some algae and sludge. They can be beneficial, but will not solve an algae problem on their own. Snails also eat plants and some snail species are worse than others. Snails can also multiply very rapidly. The common pond snail is one of the worst on both counts. Snails can clog pump intakes and plumbing lines.

What are some steps for clear water?

#1. Stop feeding your fish till the water clears! Or, at the minimum, reduce feedings to 1-2times a week (scoop out anything not eaten in 10-15 minutes). There should be plenty of natural food in the average pond for your fish to feed on.#2. Thin out your fish if you have more than one goldfish for every 50 gallons of water or one Koi for every 200-300 gallons on average. (If you can’t part with your fish, upgrade your filter to handle the extra fish- see step 5)#3. Clean out any leaves, mulch, and any other debris that has collected in the pond. As they (leaves, etc.) decompose they provide a constant flow of nutrients which feeds the algae. Net leaves before they sink to the bottom.#4. Make sure your pump is located on the opposite side of your pond as far away as possible from the waterfall stream it feeds. This ensures complete circulation throughout the pond thereby preventing stagnant areas.#5. Add the proper quantity of aquatic plants especially submerged plants and floating plants for your size pond. Place floating plants in a stream, near a pump, etc. where water is continuously pulled past their roots.#6. Add or upgrade your filter system to a 2-step system consisting of: Step 1- have a pre- filter where the pump is located and Step 2- have a proper size biological filter (example: KISS TM Filter we offer). The biological filter is best installed out of the pond and is often hidden as a waterfall.#7. Seed your pond weekly with beneficial bacteria such as Hydro-Bugs, Green-be-Gone, or Microbe-Lift PL. Dry formulas are more economical than liquids in general.#8. Add a single layer of fist-sized round stone across the bottom and on any shelves in the pond. This prevents fish from stirring up any dirt that collects on the bottom of the pond. #9. Make sure your pond is not receiving run-off from the lawn, or any surrounding ground. Raise edges a few inches with stone and foam if necessary so run-off goes around the pond instead of into the pond. #10. Do a 10-20% water change every two weeks. Be sure to purge the water from the bottom of the pond and add a dechlorinator if you use city water to refill it.

What are some common mistakes of pond owners when trying to get clear water?

  • Don’t keep draining and refilling your pond every time it begins to turn green. You will just be repeating the cycle again and again!
  • Don’t add blue or black dye if you want to grow submerged plants and be able to see your fish.
  • Don’t apply any type of algaecide or water clarifier without reading the label first. Make sure it is fish safe like PondFX or AlgaeFix. When applying algaecides to the pond make sure the water is aerated well with a pump and/or aerator.