Controlling Aquarium Algae In Fish Only Tanks

Posted in All About the Water

By Screwloose

Algae growth in an aquarium can be a frustrating and unattractive addition to the otherwise beautiful mini bio-type we as aquarist have grown to love. Some algae growth in a tank is a sign of a healthy tank and can be pleasing to the eye as a slight green shade on some rocks or driftwood. But once it starts growing rampant we often find ourselves battling to take back the ground that algae can gain rapidly.

There are certain things we can do to keep the upper hand on the algae growth in our tanks. First to under stand how to beat the algae we need to know what type of algae we are dealing with. There are several types we find in the aquarium and they all thrive in different types of water conditions. I am going to narrow this article down to the few most common we deal with.

BROWN DIATOM (aka Brown Algae)

Brown Algae feeds off of silica based rock and sands and is often the first algae seen in tanks when new substrate is added or changed. in the new set up with silica ratios higher then nutrients it will spread rapidly across the substrate and glass. It is easily removed and will disappear on its own once the ratio is balanced. It can be mechanically removed by using phosphate resin pads in a filter for a few days.

Diatom Bloom, Photo by Tom

BLUE/GREEN ALGAE (aka Slime Algae)

This type of algae is very common and easily treated. Green algae is actually cyan bacteria capable of photosynthesis. This organism can occur when there are high levels of dissolved organics and nutrients in the water. However it can also live off of nitrogen so a tank with relatively low nutrients like nitrate and phosphate can still be affected by green algae. It usually can be treated easily by increasing circulation and aeration.

Green Slime Algae, Photo by sandtiger


Hair algae is usually long and greenish or grayish in color. It is usually fueled by a combination of high nutrients and high/low lights depending on the species in particular you are dealing with. It can usually be eliminated by water changes and brighter/lower lighting. It is relatively easy to pull off of plant leaves so manual cleaning can reduce it's quantity.

Thick mass of hair algae, photo by sandtiger


Red Brush Algae prefers higher ph and kh levels then most and is theorized to utilize bicarbonates as a carbon source when nutrients are lower. Limiting the amount of phosphates and silica in the tank will deter this algae. Siamese algae eaters (crossocheilus siamensis) are a natural predator of this type as well.


I have discussed a few things that cause certain types of algae so far. Now I am going to dig into it a little deeper. In order to control algae we need to know what all the factors are that control its growth. The three main components to algae growth are lighting, food source, and temperature.


Since algae feeds from photosynthesis reducing the lighting on our tanks can sometimes be all it takes to eradicate the algae we are dealing with. Most aquariums do not require specific lighting so keeping the wattage down will help with algae control. If we limit our tank lights to 8-10 hours per day max in a fish only system we will have a better chance of winning the battle. In a planted tank 12 hours max is recommended as the plants competing for food sources will balance the lighting times. Another factor to look at is the bulb life. As the bulbs age the spectrum's change from blue to red and will promote algae growth. Replacing bulbs every six to eight months will eliminate this.

I have all my tanks set on a timer to come on right before I get home and go off after I go to bed so I can enjoy the aquarium while I am home. A simple $12.00 investment can be all it takes to control algae.

If your tank is placed in an area with a lot of natural sun light then you have a bigger factor to deal with and even though this may not be controllable, the other two factors can.


in the aquarium hobby this is usually in the form of nitrates or phosphates. Good husbandry practices and water change schedules alone can sometimes eliminate this factor thus making the life cycle for algae growth incomplete.

For those living in areas with high tds (total dissolved solids) out of the tap this can be increasingly harder. Testing your tap water for gh, kh, nitrate and phosphates will give you a good indication as to what you are up against. One of the main food sources for algae is iron. Luckily this is also the main food source for most aquarium plants that compete for the food. Sometimes planting a few plants in the tank will slow the algae growth and at the same time give the aquarium a more cosmetically appealing look.

In large cichlid tanks, it's a battle to have planted tanks but there are still options. look into some planting options that do not require rooting like hornwart.


Knowing the specific type of algae you are fighting can make all the difference in the way to counter it. Most algae thrive in warmer waters so simply reducing the temperature can slow the growth rate and allow you more time to correct any other issues that may be at play.

There are also the options for predation if your tanks bio-load will allow for it. Natural algae eaters like plecos and cae can help with minor maintenance but should not be relied on for a fail safe as often the bio-load of the fish does not justify the amount of algae removal it will provide. In short, there is nothing better then proper tank husbandry to keep your tank clean and healthy. There is no miracle cure for algae in a bottle with out the risk of killing your beneficial bacteria. Get yourself in a routine of weekly water changes that will control your bio-load and nitrate creep and watch your lighting conditions and you should have very little algae problems in your tank.