Betta (Siamese Fighting Fish) Stocking
Minimum 5 gal · 2.5" adult · low bioload · aggressive.
Estimated bioload
7%
understocked
Bioload-based: it weighs adult size and waste output, not the oversimplified "1 inch per gallon" rule.
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Keeping Betta (Siamese Fighting Fish)
The Betta (Siamese Fighting Fish) grows to about 2.5 inches and needs a minimum of 5 gallons. Its bioload is low, meaning it produces a small amount of waste for its size, a key factor the "one inch per gallon" rule ignores. It doesn't need a large group, but plan tankmates around its temperament. Temperament is aggressive, so choose tankmates carefully or keep it in a species-only setup. Use the calculator above to see how a group fits your tank's real volume before you buy.
Before you add this species
- What bioload actually isWhy a low-waste fish counts ×1 per inch
- Cycle the tank firstFishless cycling, step by step
Tanks that clear the 5-gallon minimum
Real inside dimensions and filled weight for the standard sizes that can house a Betta (Siamese Fighting Fish).
- 5 gallon tank16" × 8" × 10.5"
- 10 gallon tank20" × 10" × 12"
- 20 gallon tank24" × 12" × 16"
Species to plan alongside the Betta (Siamese Fighting Fish)
Closest on temperament and tank-size requirement. Run the whole list through the calculator before you buy: bioload adds up across species, not per species.
- Chinese Algae Eater50 gal min · 10" adult · medium bioload · aggressive
- Oscar75 gal min · 14" adult · high bioload · aggressive
- Flowerhorn Cichlid75 gal min · 15" adult · high bioload · aggressive
- Neon Tetra10 gal min · 1.5" adult · low bioload · peaceful
- Guppy10 gal min · 2" adult · low bioload · peaceful
- Southern Platy10 gal min · 2.5" adult · low bioload · peaceful
Frequently asked questions
What size tank does a Betta (Siamese Fighting Fish) need?
At least 5 gallons. They can be kept without a large group, but check tankmate compatibility.
Is the Betta (Siamese Fighting Fish) peaceful?
Temperament is aggressive. Reaching about 2.5" as an adult with a low bioload, plan tankmates and filtration accordingly.
Keep going with the same pet
Not sure of your tank's exact gallons? Measure it with the aquarium volume calculator first.
Your dog's age in human years, breed-size adjusted, not the ×7 myth.
Your cat's age in human years using the real feline curve, not the ×7 myth.
How much to feed: daily calories and cups by weight, activity and life stage.
Tank gallons and liters from your dimensions: rectangle, cylinder, hex and more.