Freshwater Aquarium Constraint Planner / no guesswork hidden

Check the habitat before adding the fish.

Review water ranges, group sizes, tank dimensions, and unresolved behavior constraints. No opaque stocking score. No false compatibility guarantee.

No sign-inLocal calculationsEditable assumptionsSource-linked methodology

Illustrative starting inputs. Replace them with your own measurements and evidence.

01 / Set your assumptions

Make it your own.

Every input stays visible and editable.

Internal tank length cm

Internal tank width cm

Internal tank height cm

Water fill height %

Substrate / decor displacement L

Cycle verified

Water temperature °C

Measured pH

Measured general hardness dGH

Measured filter flow L/h

0 records

Species and husbandry requirements

No unreviewed species catalog is presented as authoritative. Enter independently verified species-specific requirements, including social and adult-space needs.

Import CSV

Edit records Start with a row or import a CSV

Species	Quantity	Adult size cm	Minimum volume L	Minimum tank length cm	Minimum group	Minimum °C	Maximum °C	Minimum pH	Maximum pH	Minimum dGH	Maximum dGH	Behavior	Husbandry evidence	Remove

Your working plan

Make every welfare constraint visible.

Computed locally

Verify the aquarium cycle first

This is a constraint checker using your measurements and husbandry inputs, not expert approval to stock the aquarium.

Estimated water volume149 LInternal dimensions, fill fraction, and displacement

Entered livestock count0Not a stocking-capacity recommendation

Filter turnover estimate4× / hrActual entered flow; not proof of adequate filtration

Checks needing review00 species rows have no source reference

Before you act

Cycle status is not verified. Do not use this plan as a reason to add livestock. Confirm ammonia, nitrite, and stable biological filtration.
There is no inches-per-gallon rule or guaranteed safe bioload score here. Oxygen demand, filtration, adult biomass, feeding, plants, territory, and maintenance are not captured by one number.
Species ranges are user-entered and require specialist validation. Overlapping water ranges do not rule out aggression, predation, disease, or habitat mismatch.

Species-by-species constraints


No matching records. Add records or adjust your filters.

Calculation notes & limitations

Usable liters = internal length × width × height in centimeters ÷ 1,000 × fill percentage − displacement.

Each species is checked against its entered adult-space, social-group, temperature, pH, and hardness requirements. Behavior and missing evidence remain explicit warnings.

Plan name

Saving is optional. Files and records never leave your browser through this app.

02 / Look under the hood

The method is part of the tool.

Estimate actual water volume from internal dimensions, fill height, and displacement, not the nominal tank label.

Check each species against entered adult-space requirements, minimum social group, and measured water ranges.

Keep cycle status, aggression, missing husbandry evidence, and other uncertainty visible. Passing numeric checks never becomes a guaranteed compatibility score.

Read the full methodology

03 / Know the boundaries

Evidence before certainty.

Prioritize animal welfare. A specialist-reviewed husbandry plan and a properly cycled, stable aquarium are required; this calculator is not approval to add fish.

These are reference sources, not evidence that example records have been verified. Imported records retain the source links you provide.

RSPCA fish care guidance

Field notes / Tank Balance