How to Get Rid of Diatoms/Brown Algae

What are Diatoms/Brown Algae

Diatoms are typically brown in colour and are usually found in new, unestablished aquariums. They can multiply incredibly fast, making it difficult to keep the aquarium clean.


What Causes Diatom Algae?

The most common causes of diatoms are:

  1. Biologically Immature or Biologically Damaged tanks: Diatoms are most common in new tanks that are not properly cycled yet. Even if the tank is cycled and the fish are live and well, sufficient good bacteria may not have been colonised yet.

    They may also appear when well-established tanks get a deep clean. If filter media is cleaned under tap water, this can kill beneficial bacteria and crash the aquariums cycle. In doing so, diatoms may appear.

What about silicates?

Many have drawn the conclusion that diatoms are caused by high silicate levels from sand substrates. However, considering that many aquarists run diatom free aquariums with sand substrates this is unlikely true. Tap water also often contains silicates yet many aquarists run successful, diatom free aquariums on this tap water. 

How to Get Rid of Diatom Algae:

  1. Siphon: Due to its soft structure, diatoms can be easily siphoned out during water changes.
  2. Change water: Regular large water changes (50%+) in the diatom phase allows more opportunity for manual removal.
  3. Toothbrush: A toothbrush can be run gently over plants to help remove stubborn pieces.
  4. Patience: Diatoms will pass as the tank matures. Persist with manual removal and good plant care and you will overcome this stubborn algae.
  5. Algae Eaters: There are many shrimp and fish that consume diatoms and can help overcome them.

How to Prevent Diatom Algae:

  1. Dark-start your aquarium: When setting up a new aquarium, plan out your hardscape as desired, fill the tank and let it run without light until it is cycled. This dramatically reduces the chance of diatoms occurring in the first place.
  2. Discard old growth: Plants can be suffocated by diatoms. Trim off the new, healthy growth and discard old/decaying stems. This will reduce the chance of diatoms coming back.
  3. Regular water changes: If you have already planted out a new aquarium but it is not yet cycled, a strict water change schedule is recommended to prevent diatoms. Aim for 50% every day in the first week, every second day in the second week and so on.  

What Eats Diatom Algae?

Shrimp, Otocinclus, Siamese Algae Eaters and Bristlenose Catfish are all excellent consumers of diatoms. Although some shrimp species are much more effective than others. North Queensland and Darwin algae-eating shrimp and Amano shrimp are very effective. Crystal and cherry shrimp variants are attractive inhabitants but not nearly as effective.

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