How To Get Rid of Blanket Weed In My Pond

Blanket Weed in a Fish Pond

Blanket weed is an algae that plagues many ponds during the year’s warmer months. Considering that there are many ways and many products to deal with blanket weed, there’s actually a lot of confusion about which products work, how effective they are, when, and how to use them. We’re going to go through a list of products to use, breaking them down and going into detail about each one below.

Barley Straw

The first kind of product you’re going to find when dealing with blanket weed is barley straw. Barley straw typically comes in a bale of varying sizes, but you can also get the extract of barley straw, which works similarly.

The way barley straw works is as it breaks down the bacteria that is digesting, it creates hydrogen peroxide, which is very effective at preventing both hair algaes, this includes blanket weed and green water. It’s also entirely safe for use in any kind of pond and won’t affect any of its natural inhabitants, which is a benefit if you’ve got a nature pond.

Liquid barley straw is designed for use in smaller ponds, but it still works in the same way. The one negative to barley straw is that you need to use it right at the start of the year, because it takes about four to six weeks to start rotting, and only then will it start preventing the blanket weed. The best time to add it is in the springtime.


Blanket weed and algaes are facilitated by excess waste, essentially excess nutrients. Nitrates and phosphates in high levels will promote algaes. Excess nutrients in a pond is very common, and it’s normally caused by having lots of fish and feeding them frequently. Having no way of removing these excess nutrients, such as heavily planting the pond, or doing sizeable regular water changes, will also add to the issue.

The bacterial supplements are designed so that when you add these bacteria into your pond, they gobble up all the extra nutrients and out-compete the blanket weed. These products tend to be overstated and will never completely remove all your blanket weed from your pond. However, they help stabilize your pond and reduce the total amount of algae in the pond overall. Again, this product is entirely safe for nature ponds, as it is just a bacterial supplement. These bacterial supplements commonly come in powder form, but you can also get them in a liquid.


Usually, there are two types of chemicals used for combating blanket weed. The first one is the contact killer. The second one is the algaecide, which is targeted to kill algae only.

Contact Killer

This is basically a powdered form of hydrogen peroxide, with this, you water it down or apply it directly onto the algae as a powder, and through the very reactive nature of hydrogen peroxide, it will kill the algae completely. This does sound like a harsh kind of chemical to use and that’s because it is, however, within 24 hours, hydrogen peroxide will break down into water and oxygen, so it doesn’t linger around in your pond.

One problem with this chemical is you have to apply it directly, and it will burn anything it lands on. If you’ve got algae within your plants, you can have issues as it may damage the plants. Also, if it lands on any of the fish or if you’ve got frogs and other live wild creatures in your pond, it may also hurt them. That being said, it is a very cheap and effective way of killing algae. So if you’ve got algaees on your waterfalls or around the edge of your pond, where you can directly access it, then this is an excellent method to kill it because it will burn the algae to death.


These chemicals will only target algae and stop the algae from functioning, so some of them stop photosynthesis, some stop cell reproduction, and so on.

They are normally a more expensive product, however, these are a bit more direct and will definitely kill the algae you want. With these chemicals, you normally dilute them in water and then pour it straight into your pond in a good area of flow. The time of action usually is 24 hours to 48 hours. But these chemicals don’t solve the problem of why you’ve got algae in your pond, and you will need to reapply it when the algae grows back.

One thing to note with most of these chemicals is that once you’ve killed the algae, it’s all going to rot away and possibly inject a huge amount of waste into your pond. So when the algae has gone brown, the best thing to do is remove it and do a significant water change to stop any ammonia spikes and prevent a bigger algae bloom feeding on the waste products.


The last kind of product to try is the electronic blanket weed controllers. These are more of a high-end product in terms of price, and there’s lots of discussion as to whether these actually work. However, there are some good results online, and there are scientific studies to say that this technology works combating blanket weed and even green algae in the water column.

Controllers give out a radio signal into the pond, and that specific frequency will disrupt the algae’s ability to grow. This product is also safe for nature ponds. So if you’ve got a higher budget and want a permanent solution to your algae, then giving one of these controllers a try may be worth it, depending on your pond setup.

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