| What It Does | Circulates water; delivers food & O2 |
| Provided By | Powerheads / wavemakers, return pump |
| Soft/LPS | Low to moderate, indirect |
| SPS | High, turbulent, varied |
| Golden Rule | Random turbulence beats a laminar jet |
Overview
Flow is the invisible half of a healthy reef. Moving water delivers food and oxygen to corals, carries waste away, keeps detritus from settling, and prevents dead spots where cyano and detritus accumulate. Different corals want different amounts, but they all prefer turbulent, varied flow over a single blasting jet.
How Much, and What Kind
Softies and LPS like gentle-to-moderate, indirect flow — a hammer or a leather shredded by a direct powerhead is unhappy. SPS want strong, turbulent flow that keeps their branches clean and fed. Aim flow to bounce off glass and rock so it swirls, rather than pointing a powerhead straight at corals. Alternating or wave-making flow mimics the reef and keeps everything gently rocking.
Setting It Up
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- Use powerheads/wavemakers plus your return pump; total turnover of roughly 20–40x tank volume/hour is a common reef range (more for SPS).
- Position pumps to create turbulence — cross-flow, or aimed at the surface and rock, not directly into corals.
- Watch for dead spots (settling detritus, cyano film) and add/re-aim flow there.
- Keep some surface agitation — it drives gas exchange and oxygen.
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Common Mistakes
One powerhead blasting one spot: creates a sandstorm and a dead zone elsewhere — spread and vary flow. Too much direct flow on softies/LPS: they stay closed and stressed. Ignoring dead spots: that’s where nuisance films start — see our SPS care for high-flow corals.