A Helpful Guide to Algae Control and Prevention

Overgrown algae blooms are one of the most frustrating things pond owners have to face. The key to algae control is combining prevention with understanding what kind of algae you’re dealing with. In the following article, I’ll discuss the ins and outs of algae causes, control, and prevention.

Learning how to control algae takes some time but it’s not so hard when you know what you’re doing. The first thing one must understand is what causes algae blooms in the first place. 

Causes for excessive algae growth

The sun 

Sunlight accounts for most incidents of algae overgrowth. While placing a pond in a shaded area throughout daylight hours may seem like a good idea, it’s actually not. A pond needs the sun for beneficial oxygenating plant growth. Still, a pond doesn’t need sun exposure throughout the entire time that it’s out. Six to eight hours of sunlight is good. It’s not too little or too much. Remember this when it comes to pond placement.

Pond Algae | Natural Pond Lover
Common string algae

The height of algae growth peaks during the late spring throughout summer. For those living in warmer climates such as Florida, algae blooms can occur at any time of the year. While the sun is important for many things concerning a pond’s ecosystem, too much isn’t good. There are some pond tints on the market which block the sun, essentially starving it of daylight. The only problem with pond tints is they may also block the sun from beneficial submerged plants. This is why pond placement is key when taking into account the suns role in excess algae growth.

Overfeeding fish

Overfeeding pond fish is never a good idea for many reasons. One of the main reasons why pond owners shouldn’t overfeed their fish is because it often stimulates excessive algae growth. The solution to overfeeding your fish is simple. Feed them less. Only feed them enough food that nothing is floating in the water after five minutes. It’s also a good idea to remove excess uneaten food with a net. 

Excess nutrients 

Nutrients in pond lingo refer to accumulated decaying vegetation from both in and out of the water. Excess nutrients also include other matter which ends up in a pond after rainfall. These nutrients fuel algae growth in the form of excessive phosphate. Outdoor ponds can handle such nutrients to an extent. It’s when the pond becomes overloaded with them. That’s when it becomes a problem. Such nutrients cause the most trouble in the early spring when plants and beneficial bacteria are just getting restarted from their winter slumber. Having a well-balanced ecosystem minimizes algae blooms, sometimes avoiding them altogether. 

Pond inhabitants are also the cause of excessive nutrient buildup. Having too many fish and/or turtles leads to excessive ammonia levels and other sludge inducing waste. This is a reason why you shouldn’t overstock your pond with too many fish or other animals. Ducks are also messy and dirty ponds quickly. 

When it comes to fish, such as koi, 1 for every 100 gallons of water is the range to stay within.

Stagnant water 

Still, water without regular rainfall can become stagnant after a while. Having the right oxygenating plants keeps pond water from becoming stagnant when correctly set up. Still, plant growth and photosynthesis are minimal during certain times of the year. This is when algae blooms occur due to stagnated water. 

Having a waterfall or fountain helps circulate the water and breaks up algae growth. Having these add-ons also cause quicker evaporation. It’s important to understand that in the world of pond care and maintenance, fixing one issue may cause another. That’s just part of being a pond owner. 

The most common kinds of algae 

Sting algae 

Sting algae are the most common kind of algae pond owners face. This kind of algae is best described as a mass of greenish stingy, hairy, gob which tends to start out on the bottom of the pond floor quickly growing upwards to the surface. Manually remove string algae but be careful not to lose snails, tadpoles, and mosquito fish while doing so. String algae are often stubborn but once the ecosystem is running smoothly, beneficial plants which oxygenate the water outcompete them when absorbing food (nutrients). 

Green water algae 

The second most common type of algae is the kind which turns water green. Some people in the pond industry refer to this as “pea soup”. Green algae affect ponds at varying degrees. In some cases, only a light tint is visible while in more severe cases, the water is so milky you can’t see anything in it. 

In my experience, this kind of algae blooms with the changing of the seasons. It usually clears up on its own after a few weeks. While I’ve never had to take further action with it, UV filters/clarifiers are often recommended for ponds with chronic green water algae. I solve algae problems through ecosystem tweaks like adding more plants or pond inhabitants which reduce it.

Learn how to build a pond ecosystem for clear water and healthy pond inhabitants HERE. 

Natural algae prevention 


It’s important to note that while barely bales are effective in algae prevention, they’re not much use for algae control. In other words, once you have a problem, barley by itself won’t solve it. Add barley bales or barley pellets to a pond in the early spring along with a quality beneficial bacteria. When used correctly, it’s very effective in preventing frustrating and excessive algae growth. 

Pond Algae Remover | Natural Pond Lover
Two small bales of barley.


While all six of my ponds work off of natural ecosystems and not electric add-ons, I’m still able to control algae blooms when they occur. It all comes down to experience. Once you learn how a pond’s ecosystem works and what it takes to keep it balanced, algae won’t be as much of a problem to you. When I get algae blooms in my ponds, I make some simple tweaks which solve the problem. 

Using a product such as Nualgi works well and is a handy supplement. This product adds beneficial algae to the water which starves out the problematic strains. Algae blooms aren’t solved overnight no matter which method you use. Barley is great for preventing algae growth, but it doesn’t solve an established problem. This is why being proactive is the best defense against algae blooms. 

Algae causes, control, and prevention

A Helpful Guide to Algae Control and Prevention