Aquarium Filter Calculator — Flow Rate GPH & Turnover Planner
Determine ideal filter flow rate (GPH and L/h) and turnover based on tank volume, filtration type (Sponge, HOB, Canister, Sump), and fish bioload density.
Setup Parameters
Flow Rate Requirements
For a standard community aquarium, your filter should circulate 4× to 6× the total tank volume per hour (GPH = Gallons Per Hour). For example, a 20-gallon tank needs a filter rated for at least 80–120 GPH, while a 55-gallon tank needs 220–330 GPH. For heavy-waste fish like African Cichlids or Goldfish, aim for 8× to 10× turnover with a high-capacity canister filter.
Standard Aquarium Filter Flow Rate Matrix
Hourly turnover and biological media capacity recommendations across 10 standard tank sizes.
| Tank Size (Gal / L) | Gentle Flow (3–4x) | Community Flow (6–8x) | High Waste / Reef (10x+) | Recommended Bio-Media | Best Hardware Style |
|---|---|---|---|---|---|
| 5 Gallon (19 L) Nano | 15–20 GPH (60–80 L/h) | 30–40 GPH (120–150 L/h) | 50 GPH (190 L/h) | 0.25 L | Sponge Filter / Nano HOB |
| 10 Gallon (38 L) Standard | 30–40 GPH (120–150 L/h) | 60–80 GPH (230–300 L/h) | 100 GPH (380 L/h) | 0.50 L | Power HOB (AquaClear 20) |
| 20 Gallon Long (75 L) | 60–80 GPH (230–300 L/h) | 120–160 GPH (450–600 L/h) | 200 GPH (750 L/h) | 1.00 L | Large HOB or Small Canister |
| 29 Gallon (110 L) Standard | 90–120 GPH (340–450 L/h) | 180–230 GPH (680–880 L/h) | 300 GPH (1,140 L/h) | 1.50 L | Canister Filter (Fluval 207) |
| 40 Gallon Breeder (150 L) | 120–160 GPH (450–600 L/h) | 240–320 GPH (900–1,200 L/h) | 400 GPH (1,500 L/h) | 2.00 L | Canister Filter (Oase Biomaster 250) |
| 55 Gallon (208 L) Standard | 165–220 GPH (620–830 L/h) | 330–440 GPH (1,250–1,660 L/h) | 550 GPH (2,080 L/h) | 3.00 L | Canister (Fluval 307 / 407) |
| 75 Gallon (284 L) Standard | 225–300 GPH (850–1,140 L/h) | 450–600 GPH (1,700–2,270 L/h) | 750 GPH (2,840 L/h) | 4.00 L | Large Canister or Dual Filters |
| 90 Gallon (340 L) Standard | 270–360 GPH (1,020–1,360 L/h) | 540–720 GPH (2,040–2,720 L/h) | 900 GPH (3,400 L/h) | 5.00 L | Fluval FX4 / Sump Filter |
| 125 Gallon (473 L) Large | 375–500 GPH (1,420–1,900 L/h) | 750–1,000 GPH (2,840–3,780 L/h) | 1,250 GPH (4,730 L/h) | 6.00 L | Fluval FX6 / Wet-Dry Sump |
| 150 Gallon (568 L) Show | 450–600 GPH (1,700–2,270 L/h) | 900–1,200 GPH (3,400–4,540 L/h) | 1,500 GPH (5,680 L/h) | 8.00 L | Dedicated Sump System + Overflow |
Next Steps in Planning
Water Change Estimator →
Plan maintenance schedules based on your filtration capacity and bioload.
Planted Tank & CO2 Calculator →
Proper circulation ensures even CO₂ distribution throughout the tank.
Heater Sizing Calculator →
Match your heater to your filter flow rate for optimal temperature distribution.
Aquarium Filter Flow Rate Calculator — GPH, L/h & Turnover Guide.
Proper filtration keeps the water clean and oxygenated. The primary measurement is the hourly turnover rate — how many times the total water volume passes through the filter media each hour. Our aquarium filter calculator helps you find the right GPH and L/h flow for your tank size and bioload level. The filter flow rate calculator adjusts recommendations based on whether you need a canister filter, HOB, sponge filter, or sump system.
Turnover Rate Formula
Standard turnover varies by setup: Sponge filters need ~3–4x hourly turnover, Hang-on-back (HOB) and Canister filters need ~5–8x, and high-tech planted or reef systems require ~10–15x to prevent dead spots and maintain water quality.
Bioload-Driven Flow Scaling
Tanks with high bio-density accumulate ammonia rapidly. For every 40% increase in bioload above standard capacity, add 1x to the turnover rate. For heavy stocking (>80% bioload), increase turnover by 2x to prevent ammonia and nitrate spikes.
Biological Media Capacity
Your filter should hold 5–10% of the tank volume in biological media (ceramic rings, bio-balls, or matrix stones). More media surface area supports larger colonies of nitrifying bacteria, which is essential for handling high bioloads and heavy feeding schedules.
Filter Hardware Selection
Choose filter hardware that matches your tank volume and setup type. Sponge filters suit nano tanks and low-bioload breeding setups. HOB filters work well for standard community tanks (40–100 L). Canister filters provide high mechanical and biological capacity for medium to large tanks (>100 L). Sump systems are ideal for marine reefs and very large freshwater displays exceeding 250 L.
Frequently Asked Questions
Expert answers to detailed planning questions for this calculator module.
Filter Flow Sizing
How do I calculate the correct filter flow rate for my tank?
The recommended filter turnover rate is: Flow Rate (L/h) = Net Volume × Turnover Multiplier. Use 4× turnover for lightly stocked community tanks, 6× for moderately stocked tanks, 8–10× for heavily stocked or high-bioload setups, and 10–15× for cichlid tanks or sumps. Our filter flow rate calculator derives the multiplier dynamically from your stocking bioload rating and plant settings, then outputs the target L/h or GPH rating to look for when purchasing a filter.
How do I calculate filter flow rate for my aquarium?
Calculate required flow rate (in GPH or L/h) by multiplying your net tank volume by the recommended turnover multiplier. For example, a 30-gallon community tank with a 6x turnover recommendation requires a filter rated at minimum 180 GPH (680 L/h).
What is the recommended filter turnover rate for a fish tank?
Recommended hourly turnover rates vary by filter hardware and bioload: Sponge filters need 3–4x hourly volume turnover, Hang-On-Back (HOB) power filters need 5–7x, Canister filters need 6–8x, and high-tech planted or marine reef systems need 10–12x.
Does bioload increase filter flow rate requirements?
Yes. Higher bio-density produces more ammonia and organic waste. For heavy stocking (>80% bioload capacity), increase your target turnover rate by 2x to maintain adequate water oxygenation and biological conversion speed.
What size canister filter do I need for a planted aquarium?
Select a canister filter with a flow rate rated at 6x to 8x your tank volume per hour, and choose a model that holds 5% to 10% of your tank volume in biological media (e.g. ceramic rings or matrix stone).