Rain barrels are incredibly useful, turning rainfall into reliable, clean, free water that can keep your plants nourished during drought and reduce your water bill.
However, rain barrels often contain a large amount of still water, creating the perfect conditions for algae to thrive. Algae love to bloom in still water, and this can make your water smell, detracting from your garden and entertaining spaces. If the problem goes too far, it can clog your barrel, making it tricky to remove water, and in the worst cases scenario, a miniature flood in your yard.
Here, I share tips on how to prevent algae in a rain barrel, to keep your water source algae-free and clean, and also reveal the one common error to avoid that can kill your plants.
1. Regular use
The simplest way to keep algae from forming in your rain barrel is to use it regularly. Algae typically develop in standing water, so the simple act of using your rain barrel will result in movement in the surface of the water and prevent algae from forming.
Even if you fill a little watering can every few days, you'll drop the water level in the barrel and keep it moving, helping to prevent algae growth.
2. Keep the barrel out of sunlight
Algae photosynthesize, so cutting them off from sunlight will help to prevent them from growing. The easiest way to do that is by using a rain barrel with a lid - just shut the lid tight and the lack of sunlight will help to stop algae from growing. This has the added benefit of stopping algae spores from getting into your water in the first place.
If you don't have a lid, you can get a cheap rain barrel filter lid from Amazon. It will help to prevent sunlight from reaching the water, and the filter will prevent debris like leaves from falling into your water and depositing algae spores.
If this isn't possible, try to locate your rain barrel in a part of the yard that doesn't get much sun. This will help to reduce the chance of algae developing, but it means that your water may be further away from your greenhouse.
3. Keep gutters clean
Keeping your gutters clean is another way to prevent algae in your rain barrel. Leaves and other garden debris can be covered in algae spores, so leaves in your gutters can wash algae spores into your rain barrel.
The most reliable way to keep your gutters clog-free is to use gutter guards like these at Lowe's, which let water in but not leaves, pine needles, or other debris. In turn, this will stop algae from making its way into your water.
Another way around this is to use a rain chain to feed your rain barrel instead of a downspout. Rain chains use the surface tension of water to transfer rain from gutters to the ground, or in this case, a rain barrel. This means that rain chains cannot clog, because they can only carry water, which reduces the chance of leaves introducing algae to your water supply.
However, one common rain chain mistake is thinking that they can carry more water than is possible. The tradeoff, then, is that rain chains can't handle a large volume of water and not all of the rain in your gutters will make its way into your rain barrel, so they're a little inefficient.
4. Winterize your rain barrel
Winterizing your rain barrel is usually thought of as a method of preventing ice damage. If you live somewhere cold, you need to winterize your barrel, because otherwise, it will freeze solid. Water expands as it freezes into ice, and this can crack and break the barrel.
However, it's also a great way of preventing algae buildup. You don't need to use the stored water from a rain barrel in winter because it rains so much, and you won't want to go out in the rain to empty the barrel and keep the water moving. This means a lot of stagnant water, and if you aren't quick to empty it in spring when the sun and warmth return you could quickly find smelly, stagnant water. Winterizing the barrel by emptying it and turning it upside down prevents algae from forming.
This rain barrel is practical and aesthetically pleasing, appearing like an old-fashioned whiskey barrel, but it's made of durable plastic.
5. Clean once a year
Even if you don't winterize your barrel, the simple act of cleaning it can prevent algae from forming. Firstly, it gets rid of all the water algae need to bloom, entirely removing the problem.
Secondly, scrubbing down your rain barrel with a brush will remove any latent algae spores from inside the barrel, once again reducing the chance of algae in your barrel.
Cleaning a rain barrel is simple. Disconnect it from the downspout or rain chain, empty it out by watering all the plants in the yard, then scrub the barrel with a brush. If you can, don't use any cleaning products with the brush, and if you do, make sure they're rinsed off the sides. Ensure that the barrel is completely dry before you hook it back to the downspout.
This heavy duty Yonill brush is ideal for all of those tricky jobs in the yard, including scrubbing the inside of your rain barrel.
6. Avoid algaecide and vinegar
A cursory Google search about how to prevent algae in a rain barrel will give you some results which say to use algaecide or vinegar in your barrel to prevent algae. However, you should never follow this advice.
'While algaecide or vinegar will certainly kill algae in your rain barrel, it will make your water unusable,' says Head of Gardens at H&G Rachel Bull. 'While they are not plants, algae are very similar, and the same algaecide that kills them will also kill your plants.'
In short, using algaecide or vinegar on the water in your rain barrel will make all that water - in the best barrels, more than 100 gallons - toxic to your plants. If you use algaecide in your rain barrel, you could easily ruin your whole garden.
Rachel is a gardening editor, flower grower and floral designer. Her journalism career began on Country Living magazine, sparking a love of container gardening and wild planting. After more than a decade writing for and editing a range of consumer, business and special interest titles, Rachel became editor of floral art magazine The Flower Arranger. She then trained and worked as a floral designer and stylist in London for six years, before joining the Homes & Gardens team.
Learning how to prevent algae in a rain barrel is important, but this isn't the only rain barrel problem that can ruin your water supply. Rain barrels are also a magnet for mosquitos, and just like algae, your best bet is to keep the lid tightly shut, though you can also use a little vegetable oil to stop mosquitos from laying eggs and killing their larvae.
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