Silicates
Silicates are dissolved silicon compounds that can enter a reef tank primarily through incompletely purified source water or, less commonly, through certain sand or substrate types, closely associated with fueling diatom algae growth in particular. Because diatoms specifically require silicate to build their glass-like cell walls, elevated silicate levels are one of the most common underlying drivers behind the brownish diatom blooms many new reef tanks experience during their first several months.
Understanding silicates helps reef keepers correctly diagnose and address diatom outbreaks, since simply treating visible algae without addressing the underlying silicate source often leads to recurring, frustrating blooms.
Why It’s Important
- Closely associated with fueling diatom algae growth when present in excess.
- Commonly enters tanks through incompletely purified or untreated source water.
- A frequent underlying cause behind new tank diatom blooms specifically.
- Addressing the source, not just visible algae, resolves recurring outbreaks.
How It Works
Diatoms absorb dissolved silicate directly from the water column to construct their unique silica-based cell walls, meaning available silicate concentration directly limits how extensively diatom populations can bloom within a tank. RODI water with a properly functioning deionization stage removes silicate effectively, which is part of why silicate-driven diatom blooms are far less common in tanks using thoroughly purified source water.
New tanks using dry rock or certain sand types can sometimes introduce silicate directly into the water as these materials leach compounds during their initial curing period, contributing to blooms independent of source water quality.
Silicates and Related Concepts
Silicates are closely tied to diatoms, the algae most directly fueled by their presence, and to RODI water and TDS meters, the purification process and testing tool most relevant to controlling silicate input. They’re also relevant to new tank syndrome, since silicate-driven diatom blooms are a common, often overlapping early-tank phenomenon.
Reef keepers troubleshooting a persistent diatom bloom often start by testing their RODI output directly, since a failing or exhausted deionization resin is one of the most common overlooked sources of ongoing silicate input.
Diatom blooms driven by silicate typically resolve naturally within several weeks to a couple of months as available silicate is depleted, though addressing the underlying source can speed this resolution considerably.
Silicate test kits exist for reef keepers wanting to confirm this specific compound is genuinely driving an observed diatom bloom, rather than assuming based on appearance alone, particularly useful when troubleshooting a stubborn or recurring case.
Common Misconception
A common misconception is that diatom blooms are always a sign of a serious, ongoing water quality problem requiring aggressive intervention. In reality, silicate-driven diatom blooms in a new tank are often a normal, temporary phase that resolves naturally as available silicate depletes over the following weeks.
The Bottom Line
Silicates are dissolved silicon compounds closely associated with fueling diatom algae growth, particularly in new tanks. Verifying RODI water quality and addressing the underlying silicate source resolves persistent diatom blooms more effectively than treating visible algae alone.
