The two calculations
Delivered return flow ÷ net system volume. This describes how often water passes between display and sump.
Wavemaker flow is internal movement across the display. Its effect depends on direction, spread, rockwork and coral response.
A measured 1,200 l/h return on a 200-litre net system equals 6× return turnover.
Do not simply add every pump’s maximum label and call that “tank flow”. Return and powerhead flows do different jobs.
Worked return example
Suppose the display is advertised as 250 litres but the rock, sand and sump operating level leave an estimated 210 litres of actual water. If the return delivers 1,050 l/h at the outlet, turnover is 1,050 ÷ 210 = 5× per hour. That is more informative than a 3,000 l/h zero-head label on the box.
How to estimate delivered flow
Best: measure it at the return outlet with a timed container or flow meter. Next best: read the manufacturer’s pump curve at your actual head height and choose the closest pipework configuration. Worst: use maximum flow without considering lift.
What the wavemaker is for
Internal flow should keep detritus moving toward filtration, exchange water around rockwork and avoid a single harsh jet. Start conservatively, aim across or along the rockwork rather than directly at coral, and use pulsing or random modes only when they improve the actual layout.
Simple worksheet
| Input | Example | Why it matters |
|---|---|---|
| Net water volume | 210L | Use real operating volume, not the marketing capacity. |
| Return flow at outlet | 1,050L/h | Use delivered flow after lift and plumbing. |
| Return turnover | 5×/hour | Flow ÷ volume. |
| Internal circulation | Set by layout | Wavemaker label flow is not a guaranteed useful flow field. |