Getting rid of Brown Algae (diatoms) in an aquarium

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More common in newly started tanks, Brown algae is quite a nuisance and can be present in a tank for it’s entire lifespan. It primarily grows on the glass and is easily wiped off, but can also settle on ornaments or the leaves of plants and starve them of light.

The three main causes of these bacteria growing are food, light and lack of water flow:

The food source most commonly found for diatoms are the fish food your fish fail to eat. If this food remains in your tank it not only pollutes the water, it becomes food for other organisms. If you see Brown algae you are, unfortunately, likely to be overfeeding your fish.

Light is required for most life to exist and for brown algae it is essential. Your aquarium lights should not be turned on for more than 10-12 hours each day. Most people won’t want to adjust what lights they use just because of algae, but your choices are to either buy less powerful lights or to have them turned on less.

The lack of water flow can be something many people will not consider. When I first saw this in my tank it was because the filtration units I had were full of gunk and this gunk had reduced water flow in my tank. The filtration of the food waste was also impacted because of the gunk so the problem grew exponentially. Diatoms find it difficult to grow where the water flows quickly, so putting in a new filter insert (or rinsing it in tank water) can really help speed up the flow and reduce diatoms.

So basically, try feeding your fish less, try reducing lighting and try increasing water flow. If that fails, or you aren’t willing to do them, get used to scraping diatoms off the glass. If you do have to scrape, do your water changes afterwards so you can suck most of the loose debris out as you do it.

It should be noted that these are more common in new aquariums because the silicone used to seal aquariums can be a source of additional food. They can, however, grow at any time in any tank.

One thought on “Getting rid of Brown Algae (diatoms) in an aquarium

  1. Thanks Tim for this article. Rested my disturbed mind on the diatoms that were creeping across the gravel in my newly set tank.

    Will bookmark your web page to read more of your aquarium articles.

    Best regards,

    Sushil
    Hyderabad, India

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My first word was "fish", and my earliest memory is of the fish tank my parents had while I was a baby. Starting with a 10 U.S. gallon tank and easy fish like Zebra Danios, and some Cory Catfish, I quickly upgraded to 55 then 125 gallon tanks, and at one time had seven tanks in a relatively small apartment.

I've had some interesting experiences with my fish, such as moving them 1000 miles across the country and of course going through that lesson everyone needs to learn; not to trust the fish store. I've ordered fish online, but now primarily use a store called Animal Island in Midlothian, Illinois. This store accepts fish returns for partial store credit, so I have used this to my advantage and kept many different types of fish, gaining experience in a short time about a huge number of species.

My favorite fish so far is the Vulture Catfish, which is an absolutely beautiful long-whiskered and active catfish. My current biggest fish is a Fahaka Puffer.

Left: Rotkeil 'Severum'.

 
 
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Tim is British and lives in the United States with his wife and kids.

He works for software developers Image Space Inc. and Studio 397 on their racing simulations, and is a fan of Gaming, Motorsports, and photography.