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How Do I Combat String Algae in my Water Feature? – Water Feature Q & A

Picture of String Algae

Water Feature Q & A

Q: I have a 1,000 gallon pond and already the string algae is starting. I am sick of constantly cleaning it. Any ideas? – Steve of New York

A: Like Steve many of you find yourselves in this same situation, where it seems like you are battling algae year after year with no end in sight. The thing I want you to know is that in order to fully understand how to control algae, you really have to understand how it develops in the first place.

The Key Ingredient:
One of the key ingredients for algae to grow is a food source (aka Nitrates). And I’ll have to say in almost every water feature that has a bad algae problem, it is the abundant fish load that is causing the issue. So why does an abundant fish load cause algae? When fish eat they over time, like every living creature, will have to excrete the waste (aka ammonia). This ammonia, when filtered properly, will breakdown into nitrates (aka food source). Make sense so far? This food source is then eaten by algae. From there some of the algae will be eaten by the fish and thus the cycle, the nitrogen cycle of life, begins again.

So the bottom line here is: If we have control of the food source (aka Nitrates), we have control of the algae. I have mentioned this before in the past, but it bears repeating.

Keep Fish Loads to a Minimum:
I know you love your fish and this is a touchy subject. But if you plan to have sixty 12″ koi in a 1,000 gallon pond, your going to have an algae problem and it won’t be inexpensive to get a hold of. When calculating your fish load think of it in pounds of fish or total inches. For example, one 6” fish can weigh as much as four 4” fish. The number of fish will affect the overall fish load, although 10 small fish may only produce the waste of one large fish. With this said, remember that your fish are growing and in many cases multiplying. Always plan for the future and be careful not to overstock your water feature.

Proper Filtration:
The size and type of your filtration system will depend on your total fish load. If your filter is not properly sized for max potential, your fish will outgrow the filter. When this happens, ammonia levels can reach to lethal levels. In most cases filters on the market are rated for ponds containing no fish or a minimal fish load. It is always best to get a filter that is rated for at least 2x the water volume of your pond.

Aquatic Plants:
Aquatic plants and algae will compete for the same food source in order to grow. I don’t know about you, but I would much rather see a few beautiful water liles then green slime. A simple rule of thumb is to have 60% plant coverage. This should consist of submerged, floating and marginal plants. Floating plants, such as Water Hyacinths & Water Lettuce, are fantastic at pulling nitrates from the water. I recommend putting a few into your waterfall filter box if you have one. Rooted plants, such as water lilies and marginal plants, create a great place for your fish to hide from predators. Please note when aquatic plants are not present, algae will take their place. See our selection of aquatic plants here.

Beneficial Natural Bacteria :
I’m sure you hear this a lot nowadays as to why you should be adding beneficial natural bacteria to your water feature. The reason is because it is another reducer of nitrates. One  product to check out for this is called the DefensePAC. It is a combination of five products that provide beneficial bacteria, trace minerals, and a fish and plant safe pond cleaner. The DefensePAC works to breakdown fish waste, leaves or other organics that accumulate in the pond. These are essential to maintain a clean, clear and healthy ecosystem. The best of all, one DefensePAC lasts up to 6 months for a 2,000 gallon water feature.

How Do I Treat for Chara/Algae? – Pond & Lake Q & A

Picture of a bed of chara/algae

Pond & Lake Q & A

Q: How do I get rid of a chara infestation?
- Dave of Ohio

A: During the early beginnings of spring have you ever took that first stroll around the pond and discovered an awful musky smell that filled the air? That smell is chara, and it seems to take off like a wildfire during the early spring. Did you know that if you rake it out before treating it, you risk spreading it even more! So what do you do? The proper way to get rid of chara is the following:

First: Treat the chara using an algaecide
Since chara is a form of algae, using an algaecide such as Algae Defense or Hydrothol is a great way to treat for the chara. Algae Defense is best used
when there are no koi, goldfish or trout in the pond. All other fish are fine. Also there are no water use restrictions with Algae Defense. If your pond does contain koi, goldfish or trout then using Hydrothol is the way to go. The only downside with Hydrothol are its water use restrictions. Read
more about those restrictions here

Second: Wait 10 to 14 Days
The important step here is the wait the 10 to 14 days to make sure the chara has died from the algaecide treatment. Like I mentioned eariler, if you rake while the chara is still alive, it can spread.

Third & Final: Rake out the chara
Use the Airmax Pond & Beach Rake to rake out the chara from the pond. The Pond & Beach Rake includes a 25′ rope so you can throw the rake out into the pond and tug it in. I would rake the same area 2 or 3 times to make sure you removed all of the chara. Chara, fortunately is very easy to rake off of the bottom.

The other hidden benefit of raking chara, is the removal of the black muck on the bottom of the pond. This muck is a nutrient source for weeds and algae so removing it will help you that much more at maintaining the pond. Once finished with the raking, using MuckAway Pellets will help breakdown any future muck that may accumulate.

My Dog Swims in My Pond. Can I Treat for Algae? – Pond & Lake Q & A

Picture of a Dog in a Pond

Pond & Lake Q & A

Q: I have a pond that the dogs swim in almost everyday when the weather is warm. It is overrun with Algae. Is there a chemical I can use to kill the algae but not affect the dogs? – Corinne of Ohio

A: Another Great Question! I talk to quite a few pond owners who have pets that love to play in their pond and this is always a concern when it comes to treating a pond with algae. The answer is yes, there are treatments you can use to kill the algae and not harm any pets. One such product is Algae Defense.

Algae Defense is a liquid algaecide that has no “water use” restrictions such as irrigation, swimming & other recreational activities. We suggest to use Algae Defense in ponds that do not contain koi, goldfish or trout. They are very sensitive to this treatment.

If your pond does contain koi, goldfish or trout we would suggest to use a product called Hydrothol 191. The only downside are its restrictions. With dogs or other pets, we would suggest to keep them away from the pond for 7 days if possible.

Is it Too Cold to Treat My Pond for Algae? – Pond & Lake Q & A

Picture of Floating Algae

Pond & Lake Q & A

Q: I see some algae in my pond. Is it too cold to treat my pond at this point? – Jack of Ohio

A: Algae has a tendency to grow in colder temperatures even when there is ice covering your pond. To treat or not to treat really all just comes down to the temperature of the water. Algaecides, like Algae Defense (or Hydrothol if your have koi or goldfish in your pond), are most effective when water temperatures are above 50-60 degrees Fahrenheit. If you are living in the southern climates, the water temperatures may be already high enough for an algae treatment. As for the northern climates, it may be best to hold off until the water temperatures rise above the 50-60 degree Fahrenheit threshold.

Algae Growth During the Winter – Water Garden Q & A

Algae Growing in a Water Garden During Winter.

Q: I shut my water garden down for the winter, but I still see some algae growth. Can algae grow in cooler temperatures?

A: In some cases, a pond that stays clean and clear through the summer can blow up into an algal nightmare in the fall. Shutting down your watergarden ceases the flow-through characteristics of the pond. This reduces the amount of filtration that occurs both mechanically (i.e. skimmers) and biologically (i.e. filterfalls). Since there is less flow, it is a good idea to bump up the amount of bacteria in the pond by adding Seasonal Defense Bacteria with Barley. These bacteria operate in cooler conditions and will greatly reduce the amount of nutrients in the water, and also contains barley straw to naturally help with the algae. Using Oxy-Lift Defense to scrub down your rocks will also help to remove any debris build up.

Properly Getting Rid of Chara (Algae) – Pond & Lake Q & A

Picture of chara, an erected form of algae.

Q: I have been treating for Algae/Chara about every two months throughout the summer although with fall approaching (and cooler temperatures) should I still be treating it or should I wait until spring? – Paul of Michigan

A: In general we suggest that you wait until water temperatures are above 50°F: Although the real answer is that you can treat Algae/Chara anytime it is actively growing. In most cases (in the Midwest) you can start treating algae as early as March or April and continue treatment through the month of October.

Treating for Algae/Chara: Chara, although it looks like a plant is actually just an erect from of Algae.

When treating for Chara and/or floating algae always take in to consideration the following:

  • Benefits of Chara: Chara unlike planktonic and floating algae is not always an eyesore and can benefit your pond in many ways such as: naturally filtering the water, providing fish habitat, and preventing more aggressive plant grow. Chara can be selectively treated in swimming and fishing areas in larger bodies of water.
  • Treatment Area: Only treat 1/3 of your pond at a time, waiting 7-10 days between treatments to minimize oxygen depletion caused by rotting vegetation.
  • What Product Works Best: In almost every case we would suggest using liquid Algae Defense due to its cost and effectiveness. Although if your pond contains Trout, Koi or Goldfish you must test for hardness before any treatments. If the water hardness is not above 50ppm then Hydrothol 191 should be used to reduce the chance of a fish kill.
  • The Best Time of Day For Treatment: Treat early on a calm sunny day; this will give you optimal conditions for your treatments to work.

Preventive Tips:

  • Removing and/or raking dead Algae and Chara after a treatment (wait 5-7 days) can help prevent it from coming back in the future by removing excess nutrients.
  • Always consider a proactive solution over a reactive one when possible consider aeration, natural bacteria and other alternatives for a long-term solution to your problems.

There is an Oil Slick Film Covering My Pond. How Do I Get Rid of It? – Pond & Lake Q & A

Algae, Duckweed, Watermeal & Pollen Identification

Q: There is a brown rust-like film/oil slick covering my pond. Do you have an idea what this might be and how to get rid of it? - Several Customers

A: There are several things this could be: Algae, duckweed, watermeal or pollen.

Determining if Algae is a Problem: Filamentous Algae will float around the pond’s edges in mats while Planktonic Algae will make the whole body of water to look like a “pea soup” green color. If this is the case, using Algae Defense Algaecide will provide quick control. Follow up with Pond-Clear for long-term clear water.

Determining if Duckweed or Watermeal is the Problem: Duckweed and Watermeal are very rapid growers and will cover an entire pond if they get out of control. Looking to the pictures to the left, you can see that Duckweed is a small plant the size of a pencil eraser, while Watermeal is about the size of the tip of a pencil. If you determine that you have Duckweed or Watermeal, your only long-term option is WhiteCap Aquatic Herbicide. If you only require short-term control (3-4 weeks) for an event or party PondWeed Defense may be used.

Determining if Pollen is the Problem: What may look like a greenish, brownish algae, may actually be pollen. Pollen may even cause an oil-slick or film on the surface of the pond. There is no magic product that will give you a quick fix. Many times a heavy rain will settle it to the bottom. In many cases if your pond receives good circulation from an aerator or fountain you will not see pollen becoming much of a problem.

Controlling Algae in a Pond Containing Trout – Pond & Lake Q & A

Q: How do you control algae growth in a small pond that will not affect the fish (trout) in it?
-Jerry of Harrisburg, PA

A: We always suggest to customers with a pond of any size to use an aeration system along with natural bacteria to help eliminate muck and prevent stagnant water. Using these products together will make pond management easier and in time will reduce the need for chemicals. As far as the algae you currently have, there are a couple options to get rid of it. They are Algae
Defense Algaecide
and Hydrothol 191 Granular. If you use the Algae Defense, you will need to test your water hardness to ensure the carbonate hardess is above 50 ppm (parts per million) which is safe level for trout when treating with Algae Defense. If you do not wish to go that route or if your pond contains koi or goldfish, use Hydrothol 191 instead. Hydrothol 191 is a granular that will work both on algae and weeds.

Just remember, using only chemicals to control algae is a “reactive”, short-term approach. If you really want to gain control over the long-haul, then you need to be “proactive” and follow the 4-Easy Steps to the Perfect Ecosystem. Watch our 4-step video online to learn more.

Controlling Pea-Green Algae – Water Garden Q & A

Q: I have a pea-green algae problem. What is the quickest, safest way to overcome this problem? -Ruth of Starkville, MS

A: When dealing with planktonic algae or “pea-green algae”, it cannot be simply eliminated using a product like AlgaeFix. AlgaeFix works great on string algae or other patches of free-floating algae, but with planktonic algae, there is so much that you run the risk of depleting oxygen levels to a point that is unsafe for fish. One of the best ways to get rid of this type of algae is through the use of a UV Filter. As the planktonic algae passes throught the ultraviolet light, it will die. UV lights work so well that within just a few days your water will be crystal clear.


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