Free tool

Reef Flow Calculator

Flow is the most under-measured parameter in reef keeping. Tell us your tank volume and what you keep, and we will translate it into honest GPH numbers: how much your return pump should move, how much your wavemakers should add, and which equipment class fits the result.

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Step 1. Tank volume (gallons)

Step 2. What you keep

Reference

Turnover targets by coral type

Total turnover is everything moving water in the display: return pump plus wavemakers. The return alone should run 5 to 10x tank volume per hour; wavemakers supply the rest. This table works without any of the controls above.

What you keep	Total turnover target	Why
Soft coral / FOWLR	10 to 20x tank volume per hour	Softies and fish-only systems need gentle, complete circulation. Enough to keep detritus suspended, not enough to fold leather corals over.
LPS and mixed reef	20 to 30x tank volume per hour	LPS polyps feed in moderate, varied flow. Strong enough to keep the rockwork clean, indirect enough that fleshy polyps are not torn.
SPS-dominant	30 to 50x tank volume per hour	Acropora and other SPS need high randomized flow across every branch to shed mucus, deliver food, and prevent dead spots inside dense colonies.

Best Reef Tank Return Pumps and Wavemakers Return Pump and Wavemaker Guide

The calculator needs JavaScript to compute your numbers. The turnover table above works without it: multiply your tank volume by the target range for your coral type to get total GPH, size the return pump at 5 to 10x volume, and let wavemakers make up the difference.