If you own a dam or a farm pond, it’s very likely that you’ve had to deal with pond weed at some point. It is a natural result of a thriving, nutrient-rich ecosystem. But while this family of aquatic plants can provide fish with habitat and can improve water quality in moderation, too much pondweed can choke your water body and restrict swimming and boating in larger areas. And it can also reduce oxygen levels for fish.
It’s why it is so vital to keep this particular nuisance under close control.
In this article, we’ll cover everything you need to know about pondweed control. We’ll explore what it is and how it becomes a problem. And we’ll end with some of the most effective strategies for managing it in your dam or pond.
What is Pondweed?
Pondweed is a group of aquatic plants from the genus Potamogeton. They are submerged or floating-leaved plants that grow in slow-moving or still waters, including dams, ponds, lakes, and wetlands.
There are many species of pondweed, but they generally share similar characteristics, including:
- Long, flexible stems
- Narrow or broad leaves (depending on species)
- Growth from the pond bottom towards the surface
- Ability to spread quickly in the right conditions
While a small amount of pondweed is natural and even beneficial, uncontrolled growth can quickly become a problem.
How Deep Does Pondweed Grow?
Like all plants, pondweed does require sunlight in order to grow. So for very deep ponds, or for waterways that contain murky water, you’ll likely avoid the worst of the growth (excluding in the shallow areas).
Growth levels do vary depending on the species of pondweed you’re dealing with. However, growth will typically take place in ponds with a depth of between 0.5m and 3m.
In clear water, some species can establish growth in ponds as deep as 5m.
Why Does Pondweed Become a Problem?
Pondweed tends to thrive when nutrient levels are high – this is often caused by excess agricultural runoff, fertilisers, or decaying organic matter. It also grows rapidly when there are sufficient levels of sunlight to facilitate it.
When pondweed growth becomes excessive, it tends to lead to the following problems:
- Clogged waterways: Your water channels can become restrictive, leading to more difficulty with things such as swimming, fishing, and other recreational activities.
- Oxygen depletion: Too much pondweed can restrict the transfer of oxygen which can lead to lowered dissolved oxygen (DO) levels in the water. This can put strain on your fish and eventually lead to them dying out.
- Increased mosquito populations: Mosquitos thrive in areas of stagnant water around weed mats, which are caused by excess pondweed.
- Unbalanced ecosystems: Aggressive growth of pondweed (or any other dominant species for that matter) can lead to inequality in terms of resource allocation and an eventual imbalance of available plants.
Controlling Your Pondweed: Six Methods
If you’ve taken a close look at your ponds or dams and you’re starting to feel as though pondweed is becoming an issue, then you’re in luck.
At Water Quality Solutions, we’ve spent years helping people tackle these exact problems, and we’re well-versed in providing the remedies for fixing your aquatic ecosystems.
What follows are a series of methods that should help solve most issues related to pondweed. We recommend working through them in order, as you’ll be able to solve most common problems with the solutions that appear early in this list.
1. Mechanical Removal
It might sound obvious, but a bit of hard work and manual grit actually goes a long way in removing pondweed. It also helps to make any of the subsequent solutions a lot easier.
We offer two great tools to help with manually removing pondweed from your water systems. Our aquatic weed hand cutter is perfect for quickly scything through those initial surface-level weeds and those that are growing in your shallow areas. It’s non-chemical, making it perfectly safe for your fish and overall water health, and provides instant results.
You’ll also want to take on those weeds that are growing on the bottom of your dam. For this, you should check out our Beachroller tool, which rips up plants from the roots that are forming within your sludgy areas. Constructed with powder-coated aluminium and stainless steel blades, it’s built to last. And with a handle of 4.8m, you’ll be able to tackle those hard-to-reach pondweed sources with no issues at all.
2. Biological Control
Once you’ve taken out as much as you can manually, you may want to start looking into biological solutions that could help to minimise the issue in the long-term.
For this, we recommend our Biostim solution. This 100% natural, probiotic remedy helps to break down layers of sludge that build up on your dam floor. Additionally, it consumes excess nutrients to essentially starve algal blooms and weeds, restricting their growth and allowing the population of native, good plants to swell.
It comes in powder, liquid, and pellet forms and can help support long-term control and healthier water conditions.
3. Shading and Sunlight Control
Plants form in great numbers when they have access to high levels of sunlight. Consequently, another way of limiting pondweed growth is to restrict the amount of sunlight that it has access to.
We have a range of shading and sunlight control strategies to suggest, including:
- Dye: Adding a safe, non-toxic pond dye darkens the water, preventing sunlight from reaching the bottom. This reduces photosynthesis and stops pondweed from colonising deeper areas. It should be noted that this only works in deep water; weeds in shallow water will still gain access to some levels of sunlight and grow accordingly.
- Lake Bottom Blankets: Placing a physical blocker over the top of the weeds is another sure-fire way of getting rid of them. Our blankets are anchored to your dam floor with the help of thread rebar, and they come in four different sizes, making it a very versatile solution. Once your blanket has been in place for a few weeks, your area should be completely clear.
- Depth Management: You can also simply make your pond a little deeper. It might be quite labour-intensive, but you’ll have far less pondweed to deal with as light won’t be able to reach the bottom.
4. Nutrient Reduction
Pondweed flourishes in environments that have excess nutrients. So controlling where these nutrients come from is an essential tactic for minimising vegetative reproduction.
Some of the ways of reducing nutrient levels in your water systems include:
- Preventing runoff from fertilisers and animal waste
- Fencing off livestock to stock nutrient loading and bank erosion
- Applying Biostim to boost the natural microbial processes that break down organic waste
- Using an aerator to circulate water and enhance oxygen levels, which also supports beneficial bacteria that keeps nutrient levels in check
5. Aeration
Water aeration is one of the best long-term strategies for keeping aquatic weeds in check. It is a process that helps increase the levels of gas exchange at the water’s surface, thereby increasing the amount of oxygen that enters the water. This oxygenated water is then circulated evenly around your water system, preventing certain zones from growing stagnant and discouraging pondweed growth.
It also helps to increase the presence of ‘good’ bacteria, which will help to keep nutrient levels under control.
We stock a comprehensive range of high-quality aerators, suitable for just about any type of water system or size. And while aeration is great for handling this particular issue, we highly recommend its general use to help maintain overall water health.
6. Herbicide Treatments
Aquatic herbicides can be effective against pondweed. However, we offer this as a last resort as it can have negative side effects against fish and native plants.
It’s vital that you pay attention to all local regulations and closely follow label instructions should you choose to use herbicide. We also advise against using this for a whole-pond application – rather, it should be used for spot treatments when required.
If you’re looking for safe, reliable herbicides, we recommend our Water Treats Aquatic Weed Killer and our Knockout Aquatic Herbicide.
If you go the chemical route, we highly recommend you use Biostim Accelerator at the same time. Biostim Accelerator is a 100% natural biocatalyst that accelerates and improves the effectiveness of algaecides and herbicides, reducing how much chemical you need. It also degrades the decaying organic weed killed off by the herbicide, preventing it sinking to the bottom and becoming fertiliser for next season’s weed or algae bloom.
Final Thoughts
Like all weeds, pondweed is something that needs to be carefully monitored. If it’s allowed to grow unchecked, populations can explode and you can end up with a very unbalanced aquatic ecosystem that becomes increasingly difficult to turn around.
Fortunately, if you get onto things early enough, turning things around isn’t so complicated. By using a combination of the methods we’ve provided, we’re confident you’ll once again attain a healthy, balanced water body.
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