Three Reasons Your Fountain Has Algae and Their Fixes

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Most people want a crystal clear fountain full of clean water. Unfortunately, a lot of fountains end up filled with ugly algae. What gives?

Whenever there is an unusual algae bloom, there is an excess of the resources different algae nutrients. The three main sources of nutrients for algae in ponds are runoff from garden fertilizer, fish waste material, and dead leaves from nearby trees and bushes.

But what can you do to deal with the algae once it’s there? And why will these things cause algae to bloom in the first place?

Why Algae Is In Your Fountain

So, in that earlier paragraph, I was a little misleading. Virtually all water has algae in it, the algae just won’t bloom unless it has an abundance of the needed chemicals, namely phosphorous and nitrogen.

Without large amounts of these nutrients entering their ecosystem, algae will go about their lives reproducing at the usual rate and not being particularly noticeable at all.

Add in a source of nutrients that puts the ecosystem out of balance, however, and the algae will begin to reproduce rapidly. This is usually harmless to the plants and fish in your little fountain, but there are certainly times when it can become a danger.

For instance, when a large number of algae all die at once, decomposers tend to explode in population, sucking all of the oxygen out of the water and killing any fish you may be keeping.

Some kinds of algae can also end up covering the whole fountain if nothing is done to deal with them. With the fountain completely covered, your fish can end up in complete darkness, which really isn’t very good for them.

Some algae blooms can even be toxic to both fish and humans. Cyanobacteria, a kind of blue algae, can be deadly if allowed to grow in your fountain.

However, your fountain may be the decorative kind that doesn’t really have any fish.

In that case, you may just not want your fountain to look green and murky, or to have a carpet of thick, plant-like algae on top of it. In these cases, it’s critical to figure out where these extra nutrients are coming from in order to decrease the algae population in your fountain.

Plant Matter

A fountain looks like a closed system at first glance. The only thing that should be in your fountain is what you put in your fountain in theory. In reality, this is rarely true, and little things that you would never expect can lead to a change in your fountain’s ecosystem.

There are very few processes in the living world that output nitrogen, but decomposition is one of them. When dead plant matter ends up in your fountain, that gaurentees that there will be something decomposing in your fountain for quite some time to come, especially if leaves fall in in the fall and are still there in the spring.

This can cause a mass release of nitrogen into your fountain, the perfect time for algae to bloom. These blooms are usually harmless, although in a small enough fountain they can choke fish when all that agae runs out of new nitrogen and dies.

The best way to prevent this from being a problem is to keep your fountain clean as much as you possibly can.

One leaf floating on the surface of your fountain won’t cause any problems, but if there’s a tree directly above it that sheds its leaves every year around the same time, be ready to clean the leaves out of your fountain when it starts.

As a side note, if one of your fish dies it can end up causing similar problems if you allow the dead fish to remain in your pond for too long. Don’t do that. It’s gross.

Garden Fertilizer

The nutrients that algae need just so happen to be the same nutrients that plants need, meaning that anything that will fertilize a plant will also fertilize algae.

Man-made fertilizers are the most likely of these sources to cause a bloom that is harmful to the life of your pond. This is because fertilizers are designed to carry as much of these nutrients as physically possible in order to accelerate growth.

This will produce a ton of algae of whatever kind is the most common in your fountain. If there are no other living things in your fountain, this is probably your problem, and you may want to fix it before something evolves out of the increasingly thick algal bloom you’ve created.

It can be tricky to figure out where the fertilizer in your fountain is coming from. The most likely culprit is either runoff from rainwater, or runoff from when you’re watering your plants.

If the problem is the former, you may need to install a better drainage system in your garden and around your fountain to guide the runoff somewhere else.

If it is the latter, you can start by experimenting with watering your plants from a different direction. You may also want to try using a little bit less water if your plants will be okay with that.

Your plants may be right next to the fountain. In this case, you shouldn’t use any fertilizer as long as it’s avoidable. It’s best to have a twenty foot space around your fountain where you don’t use any fertilizer at all, although that may be unfeasible if you have a smaller yard.


Just like many animals, fish excretions contain nitrogen. If there isn’t anything else in your fountain eating up that nitrogen, algae will do it. If there are enough fish in the fountain, this imbalance can result in a fish kill.

However, this problem is really a problem of balance. If you find yourself with this particular, you can solve it by planting a few aquatic plants on the surface of your fountain.

These will compete with the algae for nitrogen, but more importantly they will balance out your fountain’s ecosystem.

There are some kinds of fish that will eat some kinds of algae, and these can be used as algae control if you’re in the right environment. Most of these fish are tropical, however, meaning that if you’re living in a more temperate part of the world like me these fish will only be able to stay out in the summer.

Types of Algae

The two kinds of algae most commonly found in fountains are filamentous and planktonic algae. These are both harmless in most situations. Planktonic algae will look a little bit like the water has been painted a green or blue color, while filamentous algae may look like a small mat on top of the surface.

While they are different kinds of algae, the ways to deal with them are fairly similar, although filamentous algae has enough of a form that it can be romoved trough mechanical means. This being said, because it tends to take in a lot of the most bacteria ridden materials in the water, it’s a bad idea to physically touch filamentous algae with your hands.

Taking Care of Algae

Outside of keeping fertilizer out of your fountain, the best way to take care of algae is to make sure that your fountain’s ecosystem is balanced. While the fountain may not be a completely closed system, you have control over a lot of what goes on in it. Use that control to keep everything healthy.

Floating plants like lilies and lotus are great for this, as they also provide shade for your water, limiting the amount of sunlight that the algae can get to. However, all aquatic plants are useful for limiting algae, especially if you have fish.

Some kinds of algae can be physically picked up and taken out of the pond. This is a viable short term solution, although the algae will grow back if nothing is done to take care of the excess nutrients.

One thing that you shouldn’t do is use chemical algaecides. Anything that hurts algae will hurt your fish too, and if you don’t take care of the root cause that your algae is blooming for it will just bloom again as soon as the algaecides runs out.

For a fountain that doesn’t have fish in it, algaecides can sometimes be safely used. Just be sure that the particular algaecides that you’re using is applied after you have removed the source of the nutrients that was causing the bloom in the first place, and that they won’t have any adverse affects on things near your fountain.

Remember that the algae is only a problem if there’s way too much of it. Algae is part of a healthy fountain ecosystem just as much as any of the other things living in it. Your goal isn’t to kill all of the algae, your goal is just to get the population under control.

This is less a campaign of eradication and more like pruning a tree. If the algae grow too plentiful, they’ll end up hurting themselves as well as the rest of the fountain. By keeping their population limited, you’re helping the algae to live its best life.

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We always wanted a fountain of some kind at our house, but professional installation was just too pricey. So, we decided to make our own little fountain and after learning how, we thought we should share our experiences to help people in our same situation.

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