Sump Size Calculator
A sump under 25% of your display volume is undersized by hobby standard. Get a minimum and target range before you factor in skimmer and refugium space.
Your Display Tank
Minimum sump (25% floor)
25 gal
Generous sump (40%)
40 gal
Target sump size
33 gal
accounts for standard skimmer + refugium equipment space
Why this matters: 25% of display volume is a floor, not a guarantee your equipment fits. See the Sump-to-Display Ratio Guide for why that number exists and how to calculate your own drain-back headroom. Also size your return pump to 5-10x display volume per hour before head loss, which typically nets 2-5x actual delivered turnover. Check the Return Pump Calculator for the exact math.