A couple more pics of diatoms
They are in fact beneficial and always present in a balanced tank system. According to Wikipedia, diatoms in the ocean generate 20% of the oxygen produced on the planet each year.
Diatoms are a form of photosynthetic single cell phytoplankton. While some reefers hate it, here are some fun facts on diatoms
Diatoms take up silicic acid from the water to form a silica shell (a form of glass). Sources of silicon : silica sand/quartz sand (from the beach), tap water, marine salt mix
Diatom chloroplasts (i.e. plant cell organelles that convert light energy into chemical energy via the photosynthetic process) are yellowish brown due to the presence of photosynthetic pigments such as chlorophyll (green), beta carotene (orange), and fucoxanthin (orange)
Cell walls made of silica (glass). Their exoskeleton are made of 2 halves that fit inside one another perfectly.
The walls are called frustules and have 2 main shapes – longish shape (called Pennate) and disc/cylindrical shape called centric)
Diatoms are beneficial – they can outcompete the growth of other types of algae. And prevent HAB (Harmful Algae Bloom) – green water, cyanobacteria bloom, dinoflagellates
Copepods eat phytoplankton (including diatoms) which in turn feed the fish
Note that once silicates are depleted, other forms of algae can appear. Hence a good balance is required.
Silica are in fact critical for the reef aquarium. Normal levels are 0.02ppm - 2.9ppm. Marine organisms that use silica :
Marine sponges (beneficial filter feeder) incorporate silicates in their structure.
Some mollusks (snails) have radula (teeth) to scrape off algae from rocks/glass. These teeth contain substantial silica.
And of course, diatoms - benefits mentioned above.
Credit : Pic from https://socratic.org/
In any case, if diatoms are a bother, especially when silica levels are elevated beyond the normal levels mentioned earlier, consider the following :
'Export' the silicates by siphoning out the diatoms when they form. Don't just stir or turkey baster it off the rocks/sand bed
Use aragonite sand instead of quartz/silica sand
Avoid using tap water. ICP test of tap water at Bt Batok has 1.12ppm of silicon. Use a good RODI filter to prepare water for water change & top up
Use resins such as Rowaphos (and probably other similar products). These remove plenty of phosphates but also some level of silicates.