Tannins are natural compounds that can stain water brown. They’re not harmful and they can even inhibit algae growth, but many don’t like how they look. While removal is possible, it’s costly and temporary. Aeration can improve clarity and reduce surface scums, supporting healthier water.
Summary
Understanding Tannins in Your Water
We recently did a site visit for a client — a beautiful dam at the bottom of a hill surrounded by eucalypts. It was picture perfect, except the water at the site was nearly black. If you’ve ever seen this kind of thing before, you might have wondered why it happens or if it’s dangerous.
The good news is that it’s not pollution, it’s not harmful, and it’s natural. It’s because of tannins. So let’s talk about tannins in water, why it happens, what it means… and what you can do about it.
What Are Tannins?
Tannins are natural organic compounds that leach out of leaf litter, bark, and other plant material when it decomposes in water. That’s why our client’s site had such a big tannin problem: the number of trees, especially eucalypts, around the water meant that a lot of leaves fell into the water year after year. Tannins from the leaves built up and stained the water.
It’s not always black: the colour varies depending on how much tannin there is. In mild cases, the water might look like the colour of weak tea. But in more extreme cases like this example, it can be nearly black.
Are Tannins Harmful?
Now, the thing with tannins is that they’re not inherently bad; they’re not really doing much harm. They can acidify the water slightly. One of the benefits to them is that they can act as what’s called an algae stat. An algae stat stops algae from growing. It’s quite common to have tea-stained water that is clear, but with very little or no algae. So, it can actually be a good thing.
It doesn’t look good, but it often means your dam, lake, or pond is less likely to have green scum or blooms on the surface.
Can You Remove Tannins?
You can remove tannins, but it can be expensive and impractical. You’ve got a few options available, all with benefits and challenges
– Carbon filtration: effective, but costly for larger areas
– Ozone treatment: this can oxidise tannins, but it needs specialised equipment
– Hydrogen peroxide treatment: works temporarily, but it’s not a long-term solution
It can be somewhat futile trying to remove tannins, especially considering that the tannins are going to build up again as the leaves continue to drop. You won’t get a great result if you don’t like the look of tannin-stained water.
Should You Be Worried?
Tannins aren’t dangerous. They’re part of a natural process that happens with or without human intervention. Your fish are fine — especially the Aussie natives. They’re used to living in that sort of environment. There’s nothing wrong with it or dangerous about it. You can go swimming there, fish from it, or do anything you like in it.
It’s just ugly — so if you’ve got a dam on your property and it bothers you, sorry. But if it doesn’t bother you, enjoy it.
What You Can Do
If your tannin-rich water bothers you, there is something you can do to help. Aeration can help improve overall clarity and reduce surface slicks. An aerator moves, mixes, and oxygenates the water. This makes it a healthy environment for aerobic bacteria, which are essential for breaking down organic material like leaf litter faster. This can help lighten the colour and improve overall water health.
Aeration won’t get rid of everything, but it can potentially remove some of the colour to a degree, and help clear up the water and remove some of the surface slicks and surface scums that also accompany it.
Need Help with Water Quality?
Whether you have tannin, algae, odour, or oxygenation problems, there’s a solution you can use. We work with clients all across Australia to restore balance to dams, ponds, and waterways and improve their health.
If your water’s colour or quality has changed and you want to know why, get in touch. We can help you understand what’s going on and find you a solution that fits your needs and suits your budget. Get in touch with us today to request a callback.
