Why isn’t my UV getting rid of my string algae?

One of the most common misconceptions out there in pond land is that a UV Sterilizer will help control surface algae (aka Filamentous Algae). The truth of the matter is, a UV only kills off green water (aka waterborne algae) as the algae have to pass through the UV in order to be effectively treated. The two most common forms of surface algae are Blanket Weed and Hair Algae. Blanketweed is free-floating and as it grows it will start to resemble a blanket and usually forms in clumps. Hair Algae resembles hair and attaches to just about everything in the pond. Because these algae are attached to rocks and plants, it can be a real nightmare to clean up and can affect your pond plant’s health (especially lilies).

So what causes surface algae you ask? Well it is mainly caused by a couple of things, like excessive amounts of organic waste and high levels of minerals like iron in your pond. To control surface algae, it is recommended that you do the following steps:

STEP 1. Provide a reliable biological filter that is properly sized for your pond. It is always a good rule of thumb to provide more biological filtration then what your pond calls for as you can never have too much filtration. The other thing that is important when it comes to biological filters is how they are maintained. You should never clean the biological media in your pond filter with tap water as that will kill off the beneficial bacteria that is living on the media. This goes for both well water and water from a municipality water source. What you should use to clean biological media is pond water. If you have a filter that uses foam inserts like the Laguna Pressure-Flo Series Filters, what you would want to do is take a 5 gallon bucket of pond water and squeeze each insert in that bucket several times to release the waste that is trapped on it. You want to repeat this process three times. Any biological media that is loose or in bags should be placed in a Rubbermaid container that is filled with pond water and moved around for at least two to three minutes so that you can loosen any waste that may be trapped on it. When you are finished cleaning, take the dirty water and discard. Do not pour the dirty water back into the pond.

If you have a bio waterfall, it’s a great idea to clean these (with pond water) every six weeks. A common misconception is to leave your bio falls alone and not to disturb it. The problem with that idea is that (1) sludge builds up under the mat that is being used for the mechanical filtration and will create a restriction on the waterfall’s output. (2) Waste can gradually build up on the biological media and choke off the nitrifying bacteria. It’s a great idea to take the biological media in your biofalls and rinse it real well with pond water. If you’re using lava rock in your bio falls, it’s a good idea to replace it each season with fresh lava rock. Using the same lava rock year after year is a bad idea as it will harbor dead organic waste. An excellent biological media to use in a biofall are bio spheres as they are easy to clean and are re-usable. To get the most out of your bio falls, it’s a great idea to hook up an air pump to your bio falls by running an air line with an air stone under the biological media. Doing this will increase the oxygen level to the media and that will increase the bio filter’s effectiveness.

STEP 2. Watch how often you feed your fish as this is a big contributor to the surface algae nightmare. Feed only fish foods that are high in fish meal and low in fillers as this will produce less waste. If you have a surface algae problem, it’s best to stop feeding your fish altogether and allow your pond fish to feed on the algae. Once the surface algae subsides, then begin feeding your pond fish again. When it comes to feeding your fish on a daily basis, it’s recommended that you feed them once every other day and only what they will consume in five minutes. It’s even a better idea to use a feeding point so that you can remove any uneaten food.

STEP 3. Consider using a beneficial bacteria (i.e. BioSafe’s Xtreme) in your pond as that will aid your pond filter in the breakdown of organic waste. If you have a real bad algae issue, consider using a sludge reducer (like Microbe Lift’s SA) and that will quickly digest the sludge that the surface algae is feeding on.

STEP 4. Small water changes once a month are a good thing. Simply remove 15% to 20% of the volume of your pond and then add fresh water to your pond. If you have a pressurized pond filter with backwash, it’s a great idea to perform a backwash once a week for about 30 to 45 seconds.

STEP 5. When adding water to your pond, we suggest using a dechlorinator that will also help neutralize heavy metals. Even if you have well water, it’s a great idea to do this as we are trying to neutralize metals like iron. One of the dechlorinators that do this is the PondCare Pond Chlorine & Heavy Metal Neutralizer.

STEP 6. Try and provide up to 50% pond plant coverage on your pond. Pond plants are more than just decorations, they too will also feed on the organic waste in your pond.

STEP 7. Test your water daily with a pond test kit! When it comes to algae, you want to watch Nitrates and Phosphate levels.

If you follow these seven steps, surface algae will not be a problem in your pond!

This doesn’t answer your question? email us at faq@azponds.com