Aquarium Water Flow Calculator
Created by: Ethan Brooks
Last updated:
Calculate optimal water flow and circulation for your aquarium. Get recommendations for powerhead placement, return pump sizing, and turnover rates based on your tank type and inhabitants.
Aquarium Water Flow Calculator
AquariumCalculate optimal water circulation and powerhead requirements
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What is an Aquarium Water Flow Calculator?
An Aquarium Water Flow Calculator determines the optimal water circulation for your tank based on volume, inhabitants, and aquarium type. Proper flow is essential for coral health, fish exercise, waste removal, and nutrient distribution.
This calculator provides powerhead recommendations, placement suggestions, and flow pattern guidance. Whether you're setting up a reef tank, planted aquarium, or fish-only system, correct flow makes a significant difference in overall tank health.
Flow Guidelines by Tank Type
Fish Only: 10-20x tank volume per hour. Enough for waste suspension and gas exchange.
Freshwater Planted: 5-10x turnover. Moderate flow for nutrient distribution without disturbing plants.
Soft Coral Reef: 20-30x flow. Gentle, random movement for mushrooms and leathers.
LPS Reef: 30-40x flow. Moderate turbulence for torch corals, hammers, and brains.
SPS Reef: 40-50x+ flow. Strong, random turbulence for Acropora and Montipora.
Frequently Asked Questions
How much flow does a reef tank need?
Total flow should be 20-50x tank volume per hour. Soft corals: 20-30x, LPS: 30-40x, SPS: 40-50x or more. A 100-gallon SPS tank needs 4,000-5,000 GPH total flow from all powerheads and return pump combined.
What's the difference between flow and turnover?
Turnover is how many times tank volume passes through filtration per hour (typically 4-10x). Flow is total water movement in the tank (20-50x). You need high flow for coral health but only moderate turnover for filtration.
Where should I place powerheads in my tank?
Create random, turbulent flow that reaches all areas. Place on opposite ends pointing at each other for collision. Avoid dead spots behind rocks. Wavemakers and gyres create more natural flow patterns than static powerheads.
Can you have too much flow in a reef tank?
Yes - excessive direct flow can damage coral tissue, blow sand around, and stress fish. However, high turbulent flow is fine. The goal is strong but random flow, not laminar blasts. Corals should sway gently, not be pinned down.
What size powerhead do I need?
Divide your target flow by number of powerheads. For a 100-gallon tank needing 4,000 GPH with 2 powerheads, each should be ~2,000 GPH. Controllable DC powerheads allow adjustment and are worth the investment.
Powerhead vs wavemaker vs gyre - what's the difference?
Powerheads: Traditional propeller pumps, focused flow. Wavemakers: Controllable powerheads with alternating patterns. Gyres: Wide, laminar flow creating tank-wide circulation. Most reef tanks benefit from wavemakers for variable, random flow patterns.
How much flow for a freshwater planted tank?
Much lower than reef tanks: 5-10x turnover is typical. Too much flow disturbs substrate, stresses fish, and prevents CO2 dissolution. Use spray bars or lily pipes to diffuse flow. Strong flow is only needed for hillstream setups.
Does flow affect coral growth?
Yes - proper flow delivers food and nutrients, removes waste, and prevents sediment accumulation on tissue. Insufficient flow causes tissue recession and poor polyp extension. Too much direct flow causes tissue damage. Random, moderate flow is ideal.
Sources and References
- BRS TV, "Understanding Reef Tank Flow", Bulk Reef Supply, 2024
- Reef Builders, "Powerhead Selection and Placement Guide", 2024
- Ecotech Marine, "Flow Dynamics in Reef Aquariums", 2024