How to Get Rid of Brown Algae (Diatoms) in the Fish Tank
March 17, 2022Written by: Tammy ( @aquarist_tl ) and Team Buce Plant
If you have ever kept an aquarium, then chances are you’ve run into diatoms before. Diatoms are commonly referred to as “brown algae,” one of the most common forms of algae that we see in the fishkeeping hobby that usually forms within the first month of a new tank setup.
In this blog post, we’ll go over:
2. What causes brown algae (diatoms)?
4. How do I remove brown algae?
What is "Brown Algae"?
As mentioned previously, diatoms form brown algae layers that appear in a newly set-up tank after about 1 to 3 weeks. Diatoms are single-celled organisms that technically aren’t considered species of algae. However, like plants and algae, they photosynthesize when exposed to light, and are then able to form layers and patches that cover surfaces in the tank.
Diatoms can be found in both freshwater and saltwater. You can identify brown algae if you notice a brown-colored coating on the surfaces of the glass, aquatic plants , or decorations of your aquarium. Diatoms may appear darker in color in areas of the tank that get a lot of light.
What Causes Brown Algae (Diatoms)?
Diatoms are usually the first type of “algae” that we see in our aquariums. They usually begin to appear shortly after the tank is set up because the aquarium is still cycling . Because the tank isn't balanced and the water quality/water parameters may be fluctuating, the diatoms use this to their advantage. Similar to plants, diatoms feed on nitrates and phosphates.
Nitrates are a by-product of the nitrogen cycle , in which fish waste and other decaying plant matter release ammonia and phosphates. Beneficial bacteria in the aquarium's filter media will convert the ammonia into nitrites, and then finally nitrates. If there are not enough plants in the aquarium and nitrogen levels are high, diatoms will begin to thrive. The brown algae is highly likely to flourish and spread across the surfaces of the tank, substrate , and decorations under these circumstances.
These diatoms are sometimes referred to as “silica algae”. This is because they utilize the silica in their surroundings to strengthen their cell walls. High amounts of silica in the water may be a primary cause of brown algae. Silica is often found in tap water and water from wells.
- Note: Don't be discouraged if you see brown algae, it's quite common amongst new tanks! As the tank matures and maintenance is kept up, diatom growth will decline.
Is Brown Algae Harmful?
Although considered an eye-sore, brown algae (or Diatoms) are completely harmless when it comes to the health of your fish , shrimp , and snails . Some of these species may even feed on it as a snack!
However, Diatoms can be a threat to plants if they’re left unchecked . They may coat poorly growing aquatic plants and their dying leaves, blocking the plant's source of light and eventually leaving it malnourished. This is why it's important to keep up with regular maintenance and manually remove as much as possible during the process.
How Do I Remove Brown Algae from My Aquarium?
Luckily, brown algae is pretty easy to remove from the tank. It doesn’t stay glued onto surfaces like Black Beard Algae or Blue-Green Algae . If you find Diatoms on the surface of the aquarium glass, they can easily be scraped off with an extended scraper or even an old gift card. For those that want to regularly clean the glass without getting their hands wet, there are magnetic scrapers available that make cleaning more convenient.
If the diatoms are coating the plant leaves, gently rub/brush them off with your fingers or a toothbrush. Whenever they are on tougher surfaces like rocks and stones , use a toothbrush or wire brush to scrub them off. Once you’ve polished off as much of the brown algae as possible, make sure to remove the algae and leftover debris from the tank by using a gravel vacuum or some other form of a siphon.
How Do I Get Rid Brown Algae Permanently?
Although it's known for disappearing after the tank is cycled, diatoms are an incredible eye-sore. What if there was a way to keep it from spreading, or even showing up in the first place? Here are 7 ways to prevent brown algae in the fish tank:
1. Add More Aquarium Plants!
One easy way to combat brown algae in your fish tank is to add more aquatic plants ! The plants will compete against the diatoms for essential nutrients. If the plants are kept under ideal conditions (i.e. under sufficient aquarium LED lighting , in nutrient-ric h soil , CO2 , etc.) then they have a better chance at starving off the diatoms from the nutrients.
2. Keep Up with Maintenance
Keep in mind that diatoms, otherwise known as brown algae, thrive on high nitrates. To lower the number of nitrates in the water, regular tank maintenance is key. Weekly water changes will help by replacing “old” water that may be full of nitrates with clean water. In addition, performing regular maintenance like manually removing the diatoms AND trimming/removing dead or rotting plants will prevent them from decomposing further and releasing more ammonia into the water column. Continuously gravel vacuuming or siphoning out fish waste and uneaten food is also highly recommended.
Keep in mind that diatoms thrive when a tank is not properly cycled and should go away in time as your tank balances out. To ensure your fish tank cycles quickly, keep up with regular maintenance and continuously dose nitrifying bacteria like SL-Aqua Black More Nitrifying Bacteria for Fish .
3. Consider Adding Reverse Osmosis Water
The process of reverse osmosis (RO) produces highly pure water that is free of chemicals, toxins, and water hardness. You can prime the water the be regenerated into the exact parameters you desire for your fish tank. Many hobbyists mix both conditioned tap water and RO water during water changes to create the right balance in their tank. By doing this, it helps lower the amount of nitrate and/or silica in the water, which will lower the chances of brown algae or diatoms forming in the aquarium.
3. Feed Your Fauna Less
Overfeeding is a common occurrence in the aquarium hobby. If you’re keeping up with maintenance and still see a lot of brown algae blooming, it may be because you are feeding your fauna too much. The amount of waste produced from leftover food can actually cause severe changes in the water chemistry, which allows diatoms to thrive.
Some tips to avoid overfeeding your fish tank: 1. Always feed your fish on a schedule (common is twice per day every 12 hours.) 2. Always remove uneaten fish food from the aquarium by using a siphon or gravel vacuum. 3. Add scavengers to the tank such as Loaches, Corydoras, or Nerite Snails , that will act as a cleanup crew for leftover food.
4. Increase Water Flow
The more flow you have in the tank, the harder it will be for the brown algae to latch onto surfaces and spread. If there are dead spots in the aquarium that aren’t receiving any water movement and are accumulating patches of brown algae, you can try adding a water pump or getting a stronger filter . Just make sure your tank’s inhabitants are fine with a stronger flow.
5. Add Algae-Eaters
It’s always nice to have helping hands when it comes to pesky problems like algae. Fortunately, there are a number of species of fish and invertebrates that are ready to tackle the fight against brown algae. Here’s a list of aquatic creatures that will love to eat brown algae and continuously aid in the removal of diatoms from the aquarium:
● Bristlenose Plecos
● Otocinclus Catfish
● "Pest" Snails
● Hillstream Loaches
Please remember to do research on each animal before purchasing to make sure that it will fit well with your tank’s conditions.
Green Dragon Bristlenose Plecostomus cleaning the glass
7. Maintain Proper Aquarium Lighting
Ensure that your aquarium plants are getting the right amount of light (at least 6-8 hours) and nutrients to outcompete the diatoms. The proper planted tank lighting schedule is typically no more than 8 hours and no less than 6. It has been argued that brown algae thrives in areas with low light conditions because they can easily outcompete the live plants in your tank that are struggling for resources.
I hope this information helps you to succeed in the battle against diatoms. Remember, don't be discouraged! With the proper maintenance and care, your tank will be clear of diatoms in no time. Happy fishkeeping!
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