Calculate stocking density the modern way: footprint (surface area) instead of the outdated 1-inch rule – enter species, compare both methods instantly.
The problem with 1 inch per gallon: the rule treats a 4-inch discus (deep body, high bioload, needs swimming room) the same as 4-inch neon tetras (slim body, minimal bioload). It also favors tall, narrow column tanks over wide, shallow tanks – even though the latter are better for almost all fish.
The footprint method uses length × width (cm²) as its basis. Every cm of fish body length needs a different amount of footprint depending on body size:
| Fish length | Footprint / cm | Example |
|---|---|---|
| up to 5 cm | 15 cm²/cm | Neon tetra (4 cm) → 60 cm² |
| 5–15 cm | 25 cm²/cm | Guppy (5 cm) → 125 cm² |
| over 15 cm | 40 cm²/cm | Discus (20 cm) → 800 cm² |
Note: even the footprint method is only a guideline. Territorial behavior, filtration, planting and species-specific needs can shift the value up or down. In Aqualizer this is checked per species with real database values.
Neither the 1-inch rule nor the footprint method checks whether your guppy and discus need the same pH, whether your barb is a fin-nipper, or whether the catfish hunts your shrimp at night. That takes a real database.
Predation, territorial behavior, fin-nipping – over 10,000 species combinations in the database, checked instantly whenever you add a new species.
Does your tank's pH suit the new species? Are temperature, GH and KH within tolerance? Everything compared automatically.
All the animals in your tank at a glance – count, species, date. Log losses and offspring, with full history included.
Over 2,000 species with pH, temperature, GH, KH, minimum tank size and social behavior – linked to the in-app stocking planner.
Log pH, GH, KH, NO₂, NO₃ after every water change – and instantly see whether the values suit your stocking.
Suspect an illness? Enter symptoms, get a treatment plan, and follow it step by step, day by day.
Bookmark future species. The compatibility check runs automatically against your current stock – before you buy.
No. The rule dates back to the 1950s–70s and ignores body shape, bioload and swimming space. A deep-bodied discus and a slim neon tetra aren't comparable at the same length. The footprint method (cm² of tank floor per cm of fish length) is more realistic because it favors wide, shallow tanks – matching real-world practice.
Small fish (under 5 cm) need about 15 cm² per cm of body length, medium fish (5–15 cm) about 25 cm². Example: a 100 × 40 cm tank = 4,000 cm². With small fish (4 cm, 60 cm² needed each), that's theoretically about 66 fish. Recommendation: use 60–80% of capacity, never 100%.
Not automatically. pH, temperature, GH and KH need to match for all species. Territorial behavior, predation and fin-nipping tendencies also matter. In Aqualizer, the compatibility database checks exactly that for your species combination – with a warning before you buy.
The filter can't break down the ammonia load. NO₂ rises, O₂ drops, and fish become stressed and prone to disease. Regular water changes can help temporarily, but are no permanent substitute for appropriate stocking.
For stocking density calculations: barely. The bioload of shrimp and snails is so low that 20 shrimp in a 15-gallon tank is not a problem. Snails often self-regulate based on available food.
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