Exactly what are diatoms?
While some people refer to them as "brown algae", when dealing with a freshwater aquarium, scientifically-speaking, this is not accurate, because for the most part, true brown algae thrives in a marine environment.
In short, diatoms are for the most part a form of single-celled -- or unicellular -- eukaryotic algae, although some species of diatoms can exist as colonies as well. "Eukaryotic" means that each cell contains complex structures -- such as a distinct nucleus -- which are enclosed within a membrane, or cell wall. With diatoms, this membrane is composed primarily of silica, and consists of two halves -- usually one larger than the other. This is why they are referred to as diatoms, from the Greek "diatomos", meaning "cut in two". Just like other algae, diatoms grow and reproduce through division. Some types of diatoms even possess the ability to move around by ejecting water, or through the use of a flagella.
Another interesting fact regarding diatoms is that they can float, rise or sink, depending on whether or not environmental conditions are favorable to their growth. They can even lay dormant until environmental conditions improve.
There is a widespread belief which states that diatom blooms in the aquarium are primarily related to the light level and the length of the daily photo period. However, according to what I have read, regardless of the level of light, and the length of the photo period, diatoms will bloom if the level of silicates in an aquarium is high, because, as I noted a moment ago, they use the silicates to form the two-sided, unusually-shaped membrane which surrounds their cell structures.
If one uses sand, limestone, coral rock, dolomite, or related materials in an aquarium, then chances are that initially, the silicate level will be high, which, as I said, will be extremely conducive to the growth of diatoms. For example, being as I live on an island, and my substrate is sand, and my tank is full of limestone, and our local water is hard and alkaline, I have experienced a major diatom bloom.
What some people don't realize is that even if the nitrate level in an aquarium is consistently low, as is the case with my tank -- it is always 0 to 12.5 mg/l, which is good -- they will still have problems with diatoms, because, as I said, it is the presence of silicates in the aquarium on which they thrive. Nitrate is just more fuel for the fire.
Some aquarists note that once true green algae begins to flourish in an aquarium, it will compete for food sources with the diatoms, and will eventually win over the diatoms. While there is probably some truth to this belief, I am still of the opinion that it is the silicates which diatoms need the most. To reiterate my point, no matter how high the nitrate level may be, I don't think that diatoms will flourish if there are no silicates present in the tank.
Concerning light, a high light level, and an extended photo period, only contribute more to the diatom problem, but reducing the light level, or the length of the photo period will not eliminate the diatoms entirely, it will only cause them to go dormant until conditions improve. To really rid diatoms from an aquarium, you need to work on eliminating the silicates from the tank; and frequent water changes is the best way to do that. As you may know, this is also the easiest and cheapest way to rid nitrate and other pollutants from aquarium water as well.
While scrubbing aquarium panes and decor may appear to eliminate diatoms, in reality, it is only a temporary solution. The diatoms will eventually return, unless the silicates, and nutrient sources, are removed from the aquarium environment, through consistent regular water changes, and an effective, well-maintained filtration system.
I hope that the above information is helpful to you. Just test it and see if my ideas work for you.
Regards,
TheFishGuy
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