Introduction
Many hobbyists concern themselves with elements and compounds in their water that may impact the health of their livestock, and for good reason. The effects of copper are widely known and serve as the quintessential example for removing (or preventing the addition of) harmful substances from the aquarium. However one item that has drawn some attention over the years is the collective group of silicates.
Background
Silicates are a group of compounds that contain a silicon atom and that atom is surrounded by other atoms (ligands). These ligands are usually electronegative. In the aquarium hobby we talk about oxygen bound silicates. This form of silicate is what is used in the cell wall of diatoms. Diatoms are a type of eukaryotic algae (about 100,000 species of diatoms) that are typically unwanted in the aquarium. They form a golden/brown film on the substrate and rock work and blah blah blah…
I hear the topic come up every once in a while, but for the last 15 years or so I’ve just ignored the topic. It seems to me that most hobbyists are worried about nothing.
Testing Some Tanks
I decided to pick a few aquariums to test for Silicates. They ranged in age, inhabitants, water change schedule, etc. But in the end I decided one tank in particular would sum up this investigation. I give you Shawn Winterbottom’s aquarium. This aquarium is beautiful, healthy, and has produced some very large soft coral, stony coral colonies, and huge clams over the last 5 years.
This tank is topped off with tap water… and it has NEVER had a water change. Got that? Five years, no water change, using tap water, very healthy livestock. I picked this tank because of its “high” level of silicates. The tank itself doesn’t seem to have high silicates (0.25 mg/l ), but that was as high as I could find.
Running Silicate Remover
We placed a bag of Sera Silicate Clear in the sump of this tank and then waited a month. Low and behold no more silicate. At least not enough to even register on the Sera test kit.
Other Sources of Silicates
While we didn't test other sources of silicates I will mention some places where they are found. First, and foremost, your entire glass aquarium is SiO2. These silicates are virtually insoluble according to the MSDS listings. While not soluble, glass itself can react with some of the testing methods for silicates. If a specific dye or reagent is used to bind to a silicone molecule that could effect testing- which is why some testing methods require the water to be tested in plastic vials. Anyway another source (or really non-source) of silicates is silicate sand. A rumor ran round back in the days that silicate sand (a type of quartz sand) would dissolve and leach silicates into the aquarium. Again, this is simply not the case.
One area where silicates could be introduced is in the rockwork. Some types of ceramic rock will not only release silicates but will continue to leach silicates for a long time. One of the biggest obstacles to overcome in making artificial rock is in finding a proper clay that will not leach into the water. This is why it is important for these companies to test their products and to find long term effects of their rock in reef systems. As a hobbyist it is important to buy rock that has been well tested and shown to be reef safe (like www.CeramEco.com).
Conclusion
Don’t worry about tap water silicates. While some items, such as some forms of artificial rock, can rapidly increase your silicates to harmful levels, tap water doesn't appear to be a silicate problem. The small amount of silicate from water will be used by the animals in the aquarium. Even five years of adding tap water, without a single water change, will not produce high enough levels of silicate to cause problems. If for some reason you are concerned, years down the road you can always throw a bag of silicate remover in your sump and remove the accumulated silicate. It's that easy.
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