How to Control Algae Growth in a Fish Tank: Top 6 Tips

When excessive algae growth becomes visible it can be stressful and you should focus on controlling algae growth in your fish tank. This can be a sign that the overall fish tank maintenance is either lacking or some other factors will need to be addressed. While fish tanks contain low amounts of algae, too much will cause problems.

A small amount of algae growing in your tank is normal and is part of the biological balancing process. However if not maintained it can expand and become out of control.

By becoming more pro-active on maintenance you can slow down the algae growth in most cases. Once you get control of the algae growth you can go back to your regular maintenance schedule.

In some cases, a standard maintenance schedule may not be effective enough to control large amounts of algae growth. Trial and error have found that the following tips can provide the best results to slow down the algae growth.

  • Increase tank maintenance frequency
  • Add algae eaters
  • Improve water quality
  • Regulate Lighting
  • Add Marimo moss balls to the aquarium
  • Evaluate equipment

Types of Algae

Green/Spot AlgaeToo much light and wasteAdd algae-eating fish
Red/Beard AlgaeLack of carbon dioxideApply chemical treatment such as Easy Carbon. Be careful to research plants and fish that could be affected by adding the chemical
Brown/Silica AlgaeInadequate light; New tankWill clear on its own over time by plants, tank cycling, and algae-eating fish
Blue-Green/Slime AlgaePoor water conditions; Too many nutrients such as nitrate or phosphateApply treatments to remove nitrate and phosphate
Algae Bloom/Green WaterDirect sunlight, excess nutrients, ammonia spikeBlock all light for several days

Tip 1: Increase Tank Maintenance Frequency

Clean rocks, plants, and decorations. Algae will start to show up on the items inside your tanks. These items should be removed and cleaned by removing the algae.

Soap and cleaning solutions should not be used. Only use freshwater and a scrubbing brush to clean and rinse the rocks and decoration. Plants should be gently wiped and rinsed. You will want to do this at the time of a water change.

When you cleaning the rocks, plants and decorations you will be removing them from the tank. You should take the opportunity to siphon the substrate that is below the items that are being removed for cleaning. It would also be a good time to do a water change at this time.

Clean the aquarium filters and pumps. The filter and pump equipment should be cleaned on the inside and outside of the devices. The algae will attach to the filter plastic and will need to be scrubbed off the surfaces. The filter media should be rinsed and if the algae are extreme then change out the filters. You should do this at least 2 times a week.

Remove algae from the bottom substrate (gravel and sand) The best time to do this is at each water change. Use a siphoning tool to extract the algae and debris that are collecting on the bottom of the tank. You should make sure to withdraw throughout the substrate and not just the top.

Since you will be taking out less water you may need to do this in sections at a time and eventually after 3 water changes you should be able to cover the entire tank.

Scrape algae from fish tank surface When observing your tank and notice algae on the fish tank surface you should take immediate action. You can use a magnetic cleaning tool. Be aware and purchase a cleaning tool that is made for your type of aquarium be it glass or acrylic. A couple of brands we recommend and found on Amazon are Magnetic tool for glass and Magnetic tool for acrylic.

Tip 2: Add Algae Eaters

A natural method to remove excess algae growth is to add or increase algae eating fish. Something to be aware of if you do add algae eaters and your stop the algae growth these fish will still need to have food. You can add raw vegetables such as zucchini or cucumbers. There are also algae eater wafers than can be feed to your algae eaters.

Included below are some popular algae eaters that can be added to your fish tank. Before purchasing make sure they are compatible with existing fish and will thrive in a community tank.

  • Suckermouth Catfish
  • Plecos (Plecostomus)
  • Siamese Algae Eater
  • Chinese Algae Eater
  • Octocinclus Catfish
  • Twig Catfish

Tip 3: Improve Water Quality

Decrease the amount and frequency of fish feeding. Overfeeding fish can have a negative effect on the operation of the biological cycle of your fish tank environment. The uneaten fish food will sink to the bottom and eventually increase algae growth.

You should only feed your fish in small amounts to ensure that all the food is eaten. If you find that fish food has settled to the bottom you should immediately remove it. The majority of fish will not eat the fish food once it has been deposited to the bottom of the tank.

Perform more frequent water changes. You should increase the frequency to every other day and change out 10% of the water. This should be done until you get control of the algae situation. This may need to be done for 1 to 2 weeks.

Add Water Treatments When algae growth is out of control it might be time to treat your water to remove excess nutrients that enable the algae growth. The following are some suggestions to take control of your nitrate and phosphate levels.

Tip 4: Regulate Lighting

Minimize direct sunlight When direct sunlight is in contact with your tank this can cause the algae to rapidly multiply. You should avoid all direct sunlight to your fish tank to maintain balance with algae growth. After you get your algae growth under control you should consider moving your tank or at least shielding the direct sunshine from reflecting off of your tank.

Minimize artificial light. Regulating the amount of time that your aquarium lights are on can help to keep algae growth under control. If the algae is very bad and you decide to go with a blackout you should closely monitor your live plant health. I would not do a blackout for more than 1 or 2 days since the live plants need light to grow. Some suggestions are as follows.

  • Limit light to 8 hours for fish tanks with artificial plans.
  • Limit light to 12 hours for fish tanks with live plants.
  • Do a full blackout for 1 or 2 days. You can repeat this each week so that your live plants do not suffer.

Replace fluorescent light bulbs. Over time fluorescent light bulbs will lose some of their light spectrum. When this occurs the algae in the tank will absorb

Tip 5: Add Marimo Moss Balls to the Aquarium

Marimo moss balls will help to eliminate extra nutrients that promote algae growth. Moss balls will also provide oxygen to help promote healthy fish and live plans. See our article on Marimo Moss Balls for additional details.

Tip 6: Evaluate Equipment

Add a filter pump to increase water flow in the fish tank. You can add an additional hanging filter device or a powerhead.

Replace the light bulbs in the fish tank if they are over 6 months old.

Change the filter media.

Validate the tank heater is working properly.

Control Algae Growth in Your Fish Tank

As you can see there are many factors that can produce unwanted algae growth. Doing regular maintenance is extremely important, but at times it may not be enough. Additional measures may be needed and if you follow the procedures you can see improvements quickly.

Keeping your water at optimal levels is key to a healthy tank.

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