Hello Matt. Well, I just wrote up the following and will probably be placing it on my own messageboard as well. I am beginning to believe that a significant change has been going on in my tank over the past several days. I suspect that the diatoms are starting to die off, probably because they are beginning to deplete the silicates that are in the tank, which is also being helped by the fact that I have conducted several water changes over the past week, the latest one -- about 50% of the water -- being performed about an hour ago.
Not only have the diatoms been looking sickly, and have been peeling off of the rocks more easily, but the water column itself has been filled for several days now with an abundance of minute particles, which have formed a thin white layer on the rocks as they settle. The water is NOT cloudy, or chalky white, it is just full of these minute particles, even with the filters running constantly; and I suspect that the particles are actually dead and/or dying diatoms, which do in fact float in the water column in the wild. Diatoms 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 myth which states that diatom blooms 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 they use the silicates to form the two-sided, unusually-shaped membrane which surrounds their cell.
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, it is no wonder that I have had a major diatom bloom.
What some people don't realize is that even if the nitrate level 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 that 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. You need to work on eliminating the silicates from the aquarium; and frequent water changes is the best way to do that, which is also the easiest and cheapest way to rid nitrate from a tank as well.
These are just my personal opinions, and everyone is free to disagree, as some aquarists here will probably do.
Regardless, I hope that the above information helps. Just test it and see if it is true or not.
