No products in the cart.
Return To Shop
- 0449 255 652
- FREE SHIPPING FOR ALL ORDERS OF $150
- 9:30AM - 5:00PM
- CONTACT US
- FAQS
Return to previous page
Algae in Fish ponds
Algae in Fish Ponds
What causes it and how can it be controlled?
One of the most common issues we get asked by our customers, whether in the shop or over the phone, is regarding excess algae, and pond algae treatment, especially in spring and summer. There are a few types of pond algae infestations but the common ones that usually affect ponds are blue green algae (which makes the water ‘soupy green’) and string algae (or ‘blanket weed’)
Below you will find information on the different types of pond algae, what causes it and how to keep it under control.
Table of Contents
String Algae vs Blue Green Algae
The two main types of pond algae are string algae and blue green algae.
String Algae
String algae, also known as blanket weed is a filamentous algae often appearing in the form of long, hair like strings. Sometimes when oxygen bubbles become trapped within these strings the algae can float to the surface of the pond creating a thick green mat (hence the name ‘blanket weed’). If left untreated string algae can grow very thick and long, potentially choking plants and water features.
Blue green algae is the term given to the stuff that will turn your pond water green in colour. Blue green algae is not in fact an algae at all but a type of bacteria also known as ‘cyanobacteria’. If your pond has turned green but you are unable to net any algae out, this will be the culprit.
Algae in the Aquatic Ecosystem
It must be said, that a bit of algae in a fish pond is a very normal, and often unavoidable, thing. Algae is a natural part of any aquatic ecosystem, but it can sometimes grow too much and become unsightly and might be a sign of some sort of imbalance in the pond water chemisty or conditions.
Algae grows in any water body with exposure to sunlight and more so when there are nutrients in the water. The more of either ingredient, the greater the algal growth will be.
A thin layer of algal growth on submerged surfaces such as the walls and rocks within your pond is completely normal and unavoidable (it is the reason we always say to keep ponds black and avoid lighter colours so that the green walls are not so obvious). That being said excessive string algae or green water is not the sign of a healthy pond and as such should be treated.
What causes pond algae?
Inadequate Filtration
Without an efficient filter, there is a high chance for blue algae to take a hold of your pond (especially when your pond recieves lots of sunshine). A filter is what removes waste build up from your pond and ensures healthy water parameters. Often if your pond is in full sun and does not have good filtration (including a UV filter) it will be very hard to stop it from turning green. You can read more about selecting the right filter HERE. If you’re unsure if your pond filtration is doing enough for your pond please don’t hesitate to give us a call so one our specialists can help you out.
Inadequate Water Flow (Stagnation)
Imagine a river, when it flows quickly it is usually clean and clear which is pretty to look at, but once that river slows down in the water flow, it no longer looks clean. A slow moving river will begin to look cloudy and, if it completely stops flowing, will begin to turn green.
Water flow is essential to prevent sediment from building up and allows aerobic bacteria to do their job effectively cleaning the water. This is why it is so important. Each pond will require a certain flow in order to allow the filtration to work effectively. You can read more about selecting the right pump HERE. Alternatively feel free to get into contact with one of our specialists who will gladly help you in choosing or trouble shooting the right pump for your pond.
Nitrate/Nitrites
Nitrate and Nitrite are chemicals produced by the breaking down of organic compounds such as dead leaves, fish food, etc. High nitrate/nitrite levels create excess nutrients in the water that algae love to feed off. Persistantly high levels of this chemical can cause large algal blooms that can choke up your pond system. Not to mention that they are an indication of unsafe water parameters for your fish!
You can test your water for nitrates and nitrites using a test kit which can be found HERE
Overfeeding
Fish are cold-blooded meaning that their metabolism increases and decreases based on their surrounding temperature. Therefore in winter months, fish require less feeding; and in the warmer periods a little bit more.
When you apply excess food (even if the fish eats it), it builds up and adds excess nutrients such as phosphates, nitrates and nitrites.
Becuase the fish are not making use of all of it all the time, they should only be fed what they can totally consume in about a minute or so.
Lack of oxygenation
Oxygen is essential for fish and the overall health of a pond, once anaerobic activity increases, a lot of things can go wrong such as infections, stress increase, excess nutrient build-up and ultimately, algae takeover!
A good way to control this is to keep your pond oxygenated. You can use an air pump to create bubbles for this. But if you have adequate filtration, then this might not be necessary. Visit us or give us a call and we can help point you in the right direction.
Phosphates
Phosphorus is one of those chemicals that can creep up within a fish pond or aquarium without you knowing it. It doesnt seem to affect fish health, and if you have a good filter, the water will still be clear due to the UV light sterilization.
So why are phosphates a problem in the aquatic environment? Becuase algae thrive off of it!
Phosphates tend to accumulate in ponds because biological filtration systems do not deal with them at all, which means that over time, phosphate levels incrementally increase unabated. Sources of phosphates include fish food, leaves, detritus and even tap water. The better-quality fish foods tend to release fewer phosphates. Come spring, when there are fluctuations in water temperature from warm to cool to warm and back to cool over an extended period of time it can tilt the balance of filtration in a pond which can allow algae to take a proper foothold especially the blanket weeds.
How to prevent algae in your pond
Removing phosphates
A very successful form of pond algae treatment is the removal of phosphates. Removing phosphates from your fish pond can be as simple as doing water changes or using products that will lock up the phosphates and drop them out of the solution. Doing so will make the phosphates unavailable for algal growth. A great product to put into your pond periodically is ‘Maintain for ponds’ which will bind the phosphates and add good bacteria to your pond to make it much more difficult for algae to grow.
We reccomend that all pond owners should check phosphate levels monthly so that they can ensure that levels are as close to zero at all times, especially if algae is an issue in your pond.
Using algae treatments
There are countless pond algae treatments on the market, most of which work by removing oxygen from the water therby starving the algae. It is important to remember when using algaecides to follow the dosage instructions and avoid using multiple products at once. You can see our pond algae treatments here. All of our algaecides are completely fish and plant safe (just be sure to follow the directions on the bottle), if a more natural treatment is more your speed however we have completeley natural algae solutions available as well in the form of barley straw, PondMAX 3 in 1 and all Aquascape treatments.
UV Filtration
UV (or Ultra Violet) filters are the best option when it comes to ponds that are having problems with green water. These filters can easily be added to an existing pond filtration system or can be integrated fully from the start through the use of a complete mechanical/biological filter with inbuilt UV housing such as the OASE filtoclear range.
The UV light kills single-celled algae in the pond, eliminating green water and keeping it crystal clear. The UV rays will also kill off harmful bacteria and microorganisms allowing only purified water to exit the system.
For many people, especially those with ponds in full sun, UV filtration is the ONLY thing that will reliably stop green algae from forming. Most quality pond filters will come with an inbuilt UV light which will need to be replaced every 12 months. Often you will know its time to replace your globe becuase your pond will slowly begin to loose its clarity.
If your algae problem stems from high nitrate/nitrite levels a good way to prevent it is by adding lots of water plants to your pond. Algae feeds off of these chemicals that are broken down from organic compounds such as dead leaves, fish food, etc. Plants help to rid the pond water of excess nutrients, making is inaccessible to the algae.
Water plants not only reduce nutrient loads in fish ponds, but they will also block sunlight from hitting the water, directly competing with the algae for its ingedients to survive. Speak to one of our specialists or better still, visit our store.
At The Fish Works, we stock a wide range of water plants suited for ponds at different depths and sunlight tolerence. You can read more about them HERE
All in all there are many factors that influence algae growth, be it string algae or blue green algae. As you can see, there are a multitude of factors that contribute to algal growth, so give us a call or bring in a water sample and we can try to work out the root cuase of your algal problem and treat that rather than just the symptoms. Pond owners need to discourage growth by making sure the pond is being filtrated properly with lots of water plants to take out excess nutrients and making sure dead leaves and other decaying materials are removed promptly.
If you ever need the whole pond cleaned out, then do not hesitate to call us to utilise our pond maintenance service
Above all do not overstock your pond with fish and do not overfeed!
