Brown Diatoms are very common in first two – four weeks of a new planted aquarium. It is one of the easiest to remove and keep away. Despite being called an alga by many hobbyists, Brown Diatoms are actually just diatoms, single-celled exoskeletons. These diatoms settle on aquarium glass, hardscape, and substrate surfaces, forming a light brown “dust” or layer which is fairly easy to remove by wiping.
Brown Diatoms usually appear when an newly setup aquarium has finished the nitrogen cycle process, low amounts of light, excess silica/silicates from tap water sources, excess nitrates, and/or poor aquarium maintenance. Diatoms appear especially when there are excess silicates and excess phosphates in the aquarium, which favors diatoms over other types of “lower” alga such as blue-green/slime algae or cyanobacteria. If conditions are left unresolved, other types of algae may begin to develop.
While doing a water change, wipe aquarium glass, and clean out filters. Brown diatom algae are easily removed with a paper towel or soft sponge.
Brown Diatom algae do well in low light conditions. Increasing the photoperiod gradually will prevent the diatoms from taking a foothold in your aquarium. Do not exceed 10-12 hours a day as these conditions will favor diatoms as well.
There are chemical products (such as Algone) that will neutralize silicates and phosphates. However typically you do not need to employ these methods since Brown Diatoms will disappear after cleaning and regular water changes.
Nutrients and Circulation
Reduce amount of nitrogen sources including fertilizers and fish food. In addition, if you have a heavily silicate composition in your tap water, if available, Reverse Osmosis (RO) system will prevent silicate and phosphates from entering the aquarium. There is aquarium equipment called Diatom filters which also help remove diatoms from your aquarium.
Snails and Otocinclus affinis are very good diatom eaters. However you’ll need several of each to combat a heavily diatom infested aquarium. Best to use these fauna as a preventative measure rather than a solution to brown diatoms.
In many cases, brown diatoms are an unavoidable regular occurrence for a new planted aquarium. However, performing regular water changes, and filter changes will keep brown diatoms from infecting your tank. In addition, plant your tank heavily with plants to help absorb any excess nutrients. If you tank does happen to become infected, remember once you have it, you usually don’t get it twice.