What Size Return Pump Do I Need for My Reef Tank?
Quick Answer
For most reef tanks, choose a return pump that can turn over your total system volume 5-10 times per hour after accounting for head loss from plumbing height.
Your return pump should provide 5-10x total system volume turnover per hour after accounting for head loss. For example, a 100-gallon total system (display + sump) needs 500-1000 GPH at your actual head height.
How to Calculate Return Pump Size
Step 1: Determine Total System Volume
Add your display tank and sump volumes together. For a 75-gallon display with a 20-gallon sump, your total is 95 gallons.
Step 2: Calculate Target Flow
Multiply total volume by 5-10 for your target GPH range:
- 95 gallons × 5 = 475 GPH (minimum)
- 95 gallons × 10 = 950 GPH (maximum)
Step 3: Account for Head Loss
This is critical! Pumps lose flow as water is pushed higher. Measure the vertical distance from your pump to the top of your return in the display tank. This is your "head height."
For every foot of head height plus friction from elbows and plumbing, you'll lose significant flow. Most pumps include a flow chart showing GPH at different head heights.
Example: If you need 700 GPH and have 4 feet of head height, you might need a pump rated at 1,200+ GPH at zero head.
Common Tank Sizes and Pump Recommendations
- 40-gallon system: 400-600 GPH at head
- 75-gallon system: 600-900 GPH at head
- 125-gallon system: 900-1,200 GPH at head
- 180-gallon system: 1,200-1,800 GPH at head
DC vs AC Return Pumps
DC pumps are the modern choice for most reefers:
- Adjustable flow (dial in exactly what you need)
- More energy efficient
- Run cooler, adding less heat to tank
- Often include feed modes and controllers
AC pumps are simpler but less flexible:
- Lower upfront cost
- No controller to fail
- Fixed flow rate (size carefully!)
Tips for Choosing
- Size up slightly: You can always dial down a DC pump, but you can't increase an undersized pump
- Check reviews: Real-world flow often differs from manufacturer claims
- Consider noise: Some pumps are significantly quieter than others
- Plan for growth: If you might upgrade tanks, get a pump that'll work for both
Track your tank parameters and flow adjustments using the ReefBay app to dial in the perfect circulation for your corals.
Was this helpful?
