CALCULATOR · FLOW
Reef tank flow & wavemaker calculator
The short answer
Total in-tank flow = display gallons × a turnover factor set by your corals: soft 10–20×, LPS 20–40×, SPS 40–60×, mixed 25–40×. A 75-gallon mixed reef wants 1,875–3,000 GPH, split across two opposed wavemakers rather than one big pump.
The ReefRig Flow Method
Total in-tank flow = display gallons × turnover for your corals (soft 10–20×, LPS 20–40×, SPS 40–60×, mixed 25–40×), split across two opposed pumps, not one jet.
A 75-gallon mixed reef needs 1,875–3,000 GPH of in-tank flow across two opposed wavemakers.
Total flow (GPH) by tank size and corals
In-tank flow is separate from your return pump — it’s the wavemakers only. SPS wants the most turbulent flow; soft corals the least. These are total GPH targets across all powerheads.
| Display | Soft | LPS | SPS | Mixed |
|---|---|---|---|---|
| 10 gal | 100–200 | 200–400 | 400–600 | 250–400 |
| 20 gal | 200–400 | 400–800 | 800–1,200 | 500–800 |
| 30 gal | 300–600 | 600–1,200 | 1,200–1,800 | 750–1,200 |
| 40 gal | 400–800 | 800–1,600 | 1,600–2,400 | 1,000–1,600 |
| 55 gal | 550–1,100 | 1,100–2,200 | 2,200–3,300 | 1,375–2,200 |
| 75 gal | 750–1,500 | 1,500–3,000 | 3,000–4,500 | 1,875–3,000 |
| 90 gal | 900–1,800 | 1,800–3,600 | 3,600–5,400 | 2,250–3,600 |
| 120 gal | 1,200–2,400 | 2,400–4,800 | 4,800–7,200 | 3,000–4,800 |
| 150 gal | 1,500–3,000 | 3,000–6,000 | 6,000–9,000 | 3,750–6,000 |
| 180 gal | 1,800–3,600 | 3,600–7,200 | 7,200–10,800 | 4,500–7,200 |
| 250 gal | 2,500–5,000 | 5,000–10,000 | 10,000–15,000 | 6,250–10,000 |
How many wavemakers
Two opposed pumps beat one big jet — random, colliding flow keeps detritus in suspension without sandblasting corals. Count scales with tank length.
| Tank length | Wavemakers |
|---|---|
| Up to 24 in | 1–2 |
| 24–48 in | 2–2 |
| Over 48 in | 2–3 |
LIVE CALCULATOR
Size your flow
Enter your display volume, corals and tank length. Turnover sets total GPH; tank length sets how many opposed pumps deliver it.
mixed wants 25–40× display turnover = 1875–3000 GPH total in-tank flow. Prefer 2–2 opposed pumps over one large pump — random turbulence beats a laminar jet.