Flow & turnover calculator
Your powerheads and your display volume, turned into total gph and a turnover ratio — plus a plain read of whether that lands where corals like yours usually want it.
Your powerheads
Pick a model and set roughly where you run it. Not listed? Choose “Other” and type the rated maximum off its box.
Powerheads only. If you run a sump, your return pump moves water too and is not counted here. Its real delivered flow depends on how high it has to push and how much plumbing it pushes through — a rated 1,000 gph return can deliver nearer 600 once head height, elbows and a union are in the way. Nobody publishes a curve we could apply to your plumbing, so this tool leaves it out rather than guessing at it. Read the total below as in-tank circulation from your powerheads, and treat the return as a bonus on top.
Your tank
Display volume, not system volume — turnover is conventionally quoted against the display. Rock and sand displace a real tank by roughly 10–20%, so the true figure sits a little above whatever this shows.
A compromise band: enough for the SPS up top, not so much that the LPS below stay shut.
Inside the 20-30x usually suggested for a mixed reef. How the flow is distributed still matters more than the total.
How this number is worked out
Each row is rated maximum gph × how many × average intensity, and the rows are added together. Turnover is that total divided by your display volume, in tank volumes per hour.
The return pump is not in this figure.That is a scope decision, not an oversight. A return pump's rated output is measured at zero head, and what it actually delivers falls away with every foot it lifts and every elbow, union, valve and length of pipe it pushes through — two identical pumps on two different sumps deliver materially different flow. Manufacturers publish a pump curve for head height but nothing for your particular plumbing run, so there is no honest way to fold it in here. If you want that number, read your pump's curve at your own static head and knock off a further allowance for fittings.
That linear step is the approximation. A controllable pump's real output does not track its intensity setting proportionally, and it does not fall to zero at 0% — a Tunze 6040's published floor is 53 gph, a Jebao SOW-9's is 185. No manufacturer publishes a flow curve we could cite, so this tool does one obvious, checkable approximation rather than several invented ones. Read the result as an order of magnitude, not a measurement.
The turnover bands are widely-repeated hobby guidance, not a standard. Where the flow goes matters more than how much of it there is: a tank at a “correct” turnover with every pump aimed at one rock is worse off than one below the band with the flow spread properly.
Rated maximums used above:
- EcoTech Marine VorTech MP40 QuietDrive — 4,500 gph (published spec)