Tank Answers
211 straight answers with the real computed numbers, one per question and tank size. What heater, what filter, how many fish, how much substrate, how big a water change, and the minimum tank size for popular species.
📋 Size Guides
One-page stocking and equipment plans for every standard tank size.
2.5-Gallon Tank: Stocking & Equipment Guide → 3-Gallon Tank: Stocking & Equipment Guide → 4-Gallon Tank: Stocking & Equipment Guide → 5-Gallon Tank: Stocking & Equipment Guide → 6-Gallon Tank: Stocking & Equipment Guide → 10-Gallon Tank: Stocking & Equipment Guide → 15-Gallon Tank: Stocking & Equipment Guide → 16-Gallon Tank: Stocking & Equipment Guide → 20-Gallon Tank: Stocking & Equipment Guide → 25-Gallon Tank: Stocking & Equipment Guide → 29-Gallon Tank: Stocking & Equipment Guide → 30-Gallon Tank: Stocking & Equipment Guide → 33-Gallon Tank: Stocking & Equipment Guide → 36-Gallon Tank: Stocking & Equipment Guide → 37-Gallon Tank: Stocking & Equipment Guide → 40-Gallon Tank: Stocking & Equipment Guide → 45-Gallon Tank: Stocking & Equipment Guide → 50-Gallon Tank: Stocking & Equipment Guide → 55-Gallon Tank: Stocking & Equipment Guide → 60-Gallon Tank: Stocking & Equipment Guide → 65-Gallon Tank: Stocking & Equipment Guide → 70-Gallon Tank: Stocking & Equipment Guide → 75-Gallon Tank: Stocking & Equipment Guide → 90-Gallon Tank: Stocking & Equipment Guide → 100-Gallon Tank: Stocking & Equipment Guide → 120-Gallon Tank: Stocking & Equipment Guide → 125-Gallon Tank: Stocking & Equipment Guide → 150-Gallon Tank: Stocking & Equipment Guide → 180-Gallon Tank: Stocking & Equipment Guide → 210-Gallon Tank: Stocking & Equipment Guide → 300-Gallon Tank: Stocking & Equipment Guide →
🌡️ Heater Size
The exact heater wattage each tank size needs, with one-heater or two guidance.
What Size Heater for a 2.5-Gallon Tank? → What Size Heater for a 3-Gallon Tank? → What Size Heater for a 4-Gallon Tank? → What Size Heater for a 5-Gallon Tank? → What Size Heater for a 6-Gallon Tank? → What Size Heater for a 10-Gallon Tank? → What Size Heater for a 15-Gallon Tank? → What Size Heater for a 16-Gallon Tank? → What Size Heater for a 20-Gallon Tank? → What Size Heater for a 25-Gallon Tank? → What Size Heater for a 29-Gallon Tank? → What Size Heater for a 30-Gallon Tank? → What Size Heater for a 33-Gallon Tank? → What Size Heater for a 36-Gallon Tank? → What Size Heater for a 37-Gallon Tank? → What Size Heater for a 40-Gallon Tank? → What Size Heater for a 45-Gallon Tank? → What Size Heater for a 50-Gallon Tank? → What Size Heater for a 55-Gallon Tank? → What Size Heater for a 60-Gallon Tank? → What Size Heater for a 65-Gallon Tank? → What Size Heater for a 70-Gallon Tank? → What Size Heater for a 75-Gallon Tank? → What Size Heater for a 90-Gallon Tank? → What Size Heater for a 100-Gallon Tank? → What Size Heater for a 120-Gallon Tank? → What Size Heater for a 125-Gallon Tank? → What Size Heater for a 150-Gallon Tank? → What Size Heater for a 180-Gallon Tank? → What Size Heater for a 210-Gallon Tank? → What Size Heater for a 300-Gallon Tank? →
🌀 Filter Size
Target GPH turnover and the rated filter to actually buy for each tank size.
What Size Filter for a 2.5-Gallon Tank? → What Size Filter for a 3-Gallon Tank? → What Size Filter for a 4-Gallon Tank? → What Size Filter for a 5-Gallon Tank? → What Size Filter for a 6-Gallon Tank? → What Size Filter for a 10-Gallon Tank? → What Size Filter for a 15-Gallon Tank? → What Size Filter for a 16-Gallon Tank? → What Size Filter for a 20-Gallon Tank? → What Size Filter for a 25-Gallon Tank? → What Size Filter for a 29-Gallon Tank? → What Size Filter for a 30-Gallon Tank? → What Size Filter for a 33-Gallon Tank? → What Size Filter for a 36-Gallon Tank? → What Size Filter for a 37-Gallon Tank? → What Size Filter for a 40-Gallon Tank? → What Size Filter for a 45-Gallon Tank? → What Size Filter for a 50-Gallon Tank? → What Size Filter for a 55-Gallon Tank? → What Size Filter for a 60-Gallon Tank? → What Size Filter for a 65-Gallon Tank? → What Size Filter for a 70-Gallon Tank? → What Size Filter for a 75-Gallon Tank? → What Size Filter for a 90-Gallon Tank? → What Size Filter for a 100-Gallon Tank? → What Size Filter for a 120-Gallon Tank? → What Size Filter for a 125-Gallon Tank? → What Size Filter for a 150-Gallon Tank? → What Size Filter for a 180-Gallon Tank? → What Size Filter for a 210-Gallon Tank? → What Size Filter for a 300-Gallon Tank? →
🐟 Stocking
How many fish each tank size really holds, with worked species examples.
How Many Fish in a 2.5-Gallon Tank? → How Many Fish in a 3-Gallon Tank? → How Many Fish in a 4-Gallon Tank? → How Many Fish in a 5-Gallon Tank? → How Many Fish in a 6-Gallon Tank? → How Many Fish in a 10-Gallon Tank? → How Many Fish in a 15-Gallon Tank? → How Many Fish in a 16-Gallon Tank? → How Many Fish in a 20-Gallon Tank? → How Many Fish in a 25-Gallon Tank? → How Many Fish in a 29-Gallon Tank? → How Many Fish in a 30-Gallon Tank? → How Many Fish in a 33-Gallon Tank? → How Many Fish in a 36-Gallon Tank? → How Many Fish in a 37-Gallon Tank? → How Many Fish in a 40-Gallon Tank? → How Many Fish in a 45-Gallon Tank? → How Many Fish in a 50-Gallon Tank? → How Many Fish in a 55-Gallon Tank? → How Many Fish in a 60-Gallon Tank? → How Many Fish in a 65-Gallon Tank? → How Many Fish in a 70-Gallon Tank? → How Many Fish in a 75-Gallon Tank? → How Many Fish in a 90-Gallon Tank? → How Many Fish in a 100-Gallon Tank? → How Many Fish in a 120-Gallon Tank? → How Many Fish in a 125-Gallon Tank? → How Many Fish in a 150-Gallon Tank? → How Many Fish in a 180-Gallon Tank? → How Many Fish in a 210-Gallon Tank? → How Many Fish in a 300-Gallon Tank? →
🪨 Substrate
How many pounds of gravel or sand each tank size needs for a 1 to 2 inch bed.
How Much Substrate for a 2.5-Gallon Tank? → How Much Substrate for a 3-Gallon Tank? → How Much Substrate for a 4-Gallon Tank? → How Much Substrate for a 5-Gallon Tank? → How Much Substrate for a 6-Gallon Tank? → How Much Substrate for a 10-Gallon Tank? → How Much Substrate for a 15-Gallon Tank? → How Much Substrate for a 16-Gallon Tank? → How Much Substrate for a 20-Gallon Tank? → How Much Substrate for a 25-Gallon Tank? → How Much Substrate for a 29-Gallon Tank? → How Much Substrate for a 30-Gallon Tank? → How Much Substrate for a 33-Gallon Tank? → How Much Substrate for a 36-Gallon Tank? → How Much Substrate for a 37-Gallon Tank? → How Much Substrate for a 40-Gallon Tank? → How Much Substrate for a 45-Gallon Tank? → How Much Substrate for a 50-Gallon Tank? → How Much Substrate for a 55-Gallon Tank? → How Much Substrate for a 60-Gallon Tank? → How Much Substrate for a 65-Gallon Tank? → How Much Substrate for a 70-Gallon Tank? → How Much Substrate for a 75-Gallon Tank? → How Much Substrate for a 90-Gallon Tank? → How Much Substrate for a 100-Gallon Tank? → How Much Substrate for a 120-Gallon Tank? → How Much Substrate for a 125-Gallon Tank? → How Much Substrate for a 150-Gallon Tank? → How Much Substrate for a 180-Gallon Tank? → How Much Substrate for a 210-Gallon Tank? → How Much Substrate for a 300-Gallon Tank? →
🚰 Water Changes
Weekly water change volumes and dechlorinator doses for each tank size.
Water Change for a 2.5-Gallon Tank → Water Change for a 3-Gallon Tank → Water Change for a 4-Gallon Tank → Water Change for a 5-Gallon Tank → Water Change for a 6-Gallon Tank → Water Change for a 10-Gallon Tank → Water Change for a 15-Gallon Tank → Water Change for a 16-Gallon Tank → Water Change for a 20-Gallon Tank → Water Change for a 25-Gallon Tank → Water Change for a 29-Gallon Tank → Water Change for a 30-Gallon Tank → Water Change for a 33-Gallon Tank → Water Change for a 36-Gallon Tank → Water Change for a 37-Gallon Tank → Water Change for a 40-Gallon Tank → Water Change for a 45-Gallon Tank → Water Change for a 50-Gallon Tank → Water Change for a 55-Gallon Tank → Water Change for a 60-Gallon Tank → Water Change for a 65-Gallon Tank → Water Change for a 70-Gallon Tank → Water Change for a 75-Gallon Tank → Water Change for a 90-Gallon Tank → Water Change for a 100-Gallon Tank → Water Change for a 120-Gallon Tank → Water Change for a 125-Gallon Tank → Water Change for a 150-Gallon Tank → Water Change for a 180-Gallon Tank → Water Change for a 210-Gallon Tank → Water Change for a 300-Gallon Tank →
📏 Species Minimums
The minimum tank size for popular freshwater species, with tankmates.
Betta Minimum Tank Size → Neon Tetra Minimum Tank Size → Cardinal Tetra Minimum Tank Size → Guppy Minimum Tank Size → Platy Minimum Tank Size → Molly Minimum Tank Size → Swordtail Minimum Tank Size → Zebra Danio Minimum Tank Size → Harlequin Rasbora Minimum Tank Size → Cherry Barb Minimum Tank Size → Tiger Barb Minimum Tank Size → Corydoras Minimum Tank Size → Otocinclus Minimum Tank Size → Bristlenose Pleco Minimum Tank Size → Dwarf Gourami Minimum Tank Size → Pearl Gourami Minimum Tank Size → Angelfish Minimum Tank Size → Discus Minimum Tank Size → German Blue Ram Minimum Tank Size → Kribensis Minimum Tank Size → Goldfish Minimum Tank Size → Cherry Shrimp Minimum Tank Size → Amano Shrimp Minimum Tank Size → Mystery Snail Minimum Tank Size → Kuhli Loach Minimum Tank Size →
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