# Aquarium Calculators

> Free, source-linked calculators for community tanks and planted setups — compatibility, water chemistry, filtration, stocking, lifecycle, and feeding.

- [Browse all 33 aquarium tools](#tools)
- [Browse all pet care tools](/tools/)
- [About](/about/)
- [Sources](/sources/)

## All aquarium tools

- **[Aquarium Fish Compatibility Checker](https://petguidecalc.com/aquarium/mix-calculator/)** — Compatibility verdicts with reasons for 12 common freshwater community fish, based on temperature and temperament rules. _(Reviewed 2026-08)_
- **[Aquarium Water Change Schedule](https://petguidecalc.com/aquarium/water-change-scheduler/)** — Water-change cadence and volume by load level: light 10%/2 weeks, standard 20%/2 weeks, heavy 30%/week (Co-Op + Instant Ocean). _(Reviewed 2026-09)_
- **[Aquarium Salinity & Salt Mix](https://petguidecalc.com/aquarium/salinity-calculator/)** — Instant Ocean salt grams from tank volume and target SG; built-in SG↔ppt conversion and a refractometer cross-check. _(Reviewed 2026-09)_
- **[Rectangular Aquarium Volume Calculator](https://petguidecalc.com/aquarium/volume-calculator/)** — Water volume of a rectangular tank from length, width, and height in cm or inches, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Cube Aquarium Volume Calculator](https://petguidecalc.com/aquarium/cube-aquarium-volume-calculator/)** — Water volume of a cube aquarium from its side length, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Breeder Aquarium Volume Calculator](https://petguidecalc.com/aquarium/breeder-aquarium-volume-calculator/)** — Water volume of a low-profile breeder tank from length, width, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Shallow Aquarium Volume Calculator](https://petguidecalc.com/aquarium/shallow-aquarium-volume-calculator/)** — Water volume of a shallow rectangular tank from length, width, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Bow-Front Aquarium Volume Calculator](https://petguidecalc.com/aquarium/bow-front-aquarium-volume-calculator/)** — Water volume of a bow-front tank from length, flat depth, bow depth, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Cylinder Aquarium Volume Calculator](https://petguidecalc.com/aquarium/cylinder-aquarium-volume-calculator/)** — Water volume of a cylindrical tank from radius and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Half-Cylinder Aquarium Volume Calculator](https://petguidecalc.com/aquarium/half-cylinder-aquarium-volume-calculator/)** — Water volume of a half-cylinder tank from radius and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Elliptical Aquarium Volume Calculator](https://petguidecalc.com/aquarium/elliptical-aquarium-volume-calculator/)** — Water volume of an elliptical tank from the semi-major and semi-minor axes and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Bullnose Aquarium Volume Calculator](https://petguidecalc.com/aquarium/bullnose-aquarium-volume-calculator/)** — Water volume of a bullnose tank from length, width, corner radius, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Round-End Aquarium Volume Calculator](https://petguidecalc.com/aquarium/round-end-aquarium-volume-calculator/)** — Water volume of a round-end tank from length, width, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Corner Bow-Front Aquarium Volume Calculator](https://petguidecalc.com/aquarium/corner-bow-front-aquarium-volume-calculator/)** — Water volume of a corner bow-front tank from length, flat depth, bow depth, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Corner Cylinder Aquarium Volume Calculator](https://petguidecalc.com/aquarium/corner-cylinder-aquarium-volume-calculator/)** — Water volume of a corner cylinder tank from radius and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Corner Prism Aquarium Volume Calculator](https://petguidecalc.com/aquarium/corner-prism-aquarium-volume-calculator/)** — Water volume of a corner prism tank from the two wall legs and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Hexagon Aquarium Volume Calculator](https://petguidecalc.com/aquarium/hexagon-aquarium-volume-calculator/)** — Water volume of a hexagonal tank from side length and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Flat-Back Hexagon Aquarium Volume Calculator](https://petguidecalc.com/aquarium/flat-back-hexagon-aquarium-volume-calculator/)** — Water volume of a flat-back hexagon tank from front panel width, depth, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Octagon Aquarium Volume Calculator](https://petguidecalc.com/aquarium/octagon-aquarium-volume-calculator/)** — Water volume of an octagonal tank from side length and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Pentagon Aquarium Volume Calculator](https://petguidecalc.com/aquarium/pentagon-aquarium-volume-calculator/)** — Water volume of a pentagonal tank from side length and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[L-Shaped Aquarium Volume Calculator](https://petguidecalc.com/aquarium/l-shaped-aquarium-volume-calculator/)** — Water volume of an L-shaped tank from the two section dimensions and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Trapezoid Aquarium Volume Calculator](https://petguidecalc.com/aquarium/trapezoid-aquarium-volume-calculator/)** — Water volume of a trapezoid tank from front base, back base, depth, and height, with fill-height and substrate corrections and freshwater/saltwater weight. _(Reviewed 2026-09)_
- **[Fish Bowl Volume Calculator](https://petguidecalc.com/aquarium/fish-bowl-aquarium-volume-calculator/)** — Water volume of a spherical fish bowl from its diameter, with a welfare note on small bowls. _(Reviewed 2026-09)_
- **[Aquarium Volume Unit Converter](https://petguidecalc.com/aquarium/volume-unit-converter/)** — Convert aquarium volumes between US gallons, liters, UK gallons, cubic inches, cubic feet, and cubic centimeters with live results. _(Reviewed 2026-09)_
- **[Aquarium Water Displacement Calculator](https://petguidecalc.com/aquarium/water-displacement-calculator/)** — Actual water volume after substrate, live rock, equipment, and air space, using labeled void-fraction defaults. _(Reviewed 2026-09)_
- **[Aquarium Sump Volume Calculator](https://petguidecalc.com/aquarium/sump-volume-calculator/)** — Total system water volume from display tank, sump chamber, and refugium, with a hobby sump sizing table. _(Reviewed 2026-09)_
- **[Aquarium Substrate Calculator](https://petguidecalc.com/aquarium/substrate-calculator/)** — Sand, gravel or aquasoil volume in liters and weight in kg/lb from tank length, width and substrate depth, with density presets. _(Reviewed 2026-09)_
- **[Aquarium Heater Wattage Calculator](https://petguidecalc.com/aquarium/heater-wattage/)** — Starting heater wattage in W from tank size, temperature rise in °F, and room temperature, rounded to common 25–300 W heater steps. _(Reviewed 2026-09)_
- **[Aquarium Filter Flow Calculator](https://petguidecalc.com/aquarium/filter-flow/)** — Recommended filter flow in GPH from tank volume, filter type, and freshwater vs saltwater, with a 70% head-loss note. _(Reviewed 2026-09)_
- **[Aquarium Nitrogen Cycle Tracker](https://petguidecalc.com/aquarium/nitrogen-cycle/)** — Verdict on ammonia, nitrite, and nitrate readings — UNSAFE, CYCLING, ESTABLISHED, or WATER-CHANGE-DUE — with the next step. _(Reviewed 2026-09)_
- **[Aquarium Quarantine Duration Calculator](https://petguidecalc.com/aquarium/quarantine-duration/)** — Recommended quarantine window in days from tank temperature in °F and risk profile (standard, wild-caught, sick-tank history). _(Reviewed 2026-09)_
- **[Aquarium Feeding Amount Calculator](https://petguidecalc.com/aquarium/feeding-amount/)** — Per-feeding portion and meals per day from adult size class, life stage, and food type, with the 5-minute rule of thumb. _(Reviewed 2026-09)_
- **[Red-Eared Slider Water Temperature Checker](https://petguidecalc.com/aquarium/red-eared-slider-temperature/)** — Check water (24–29 °C), basking (24–31 °C), night (18–24 °C), water depth (1.5–2× shell), and minimum tank volume (10 gal/inch). _(Reviewed 2026-09)_

## How the numbers work

Aquarium calculations draw on three sources of authority: species profiles from SeriouslyFish and FishBase for temperature ranges, minimum tank size, and temperament; standard community-tank rules for filtration turnover (typically 4–6× tank volume per hour for freshwater, higher for saltwater); and the established ammonia → nitrite → nitrate nitrogen cycle that any cycled tank follows.

Every tool names its sources inline on its own page. The complete enumeration is on [/sources/](/sources/), and the methodology (how accuracy and review cadence are handled) is on [/methodology/](/methodology/).

## Aquarium calculator questions

### How do I know whether two fish are compatible?

The aquarium compatibility checker cross-references temperature class (tropical vs coldwater), minimum tank size, and documented predation or aggression patterns for 12 common community species. For pairs outside that list, the answer is "conditional" by default — meaning the pair can work in a large, well-planted tank with careful monitoring.

### How often should I do a water change, and how much?

The water change scheduler uses your bioload (light, standard, or heavy) to recommend a percent-and-cadence combo: light 10% every two weeks, standard 20% every two weeks, heavy 30% weekly. Filter maintenance and plant pruning can shift the schedule in either direction; the calculator flags the inputs that affect the answer.

### What does the nitrogen cycle calculator actually do?

It reads your ammonia, nitrite, and nitrate test results and returns a verdict: UNSAFE (immediate action), CYCLING (still establishing bacteria), ESTABLISHED (parameters within target), or WATER-CHANGE-DUE (nitrate climbed above the safe band). Useful at every stage of a new tank and as a sanity check during regular maintenance.

### Why does my heater wattage recommendation differ from the box label?

Manufacturer wattage ratings assume ideal room temperature and a fully insulated lid. The heater wattage calculator uses tank volume, the temperature rise you need in °F, and room temperature to round to the next standard 25/50/75/100/150/200/250/300 W step. It will often recommend slightly more wattage than the box label if your room runs cool.

### How much should I feed my fish?

The feeding amount calculator returns a per-feeding portion wording and meals-per-day figure, scaled to the adult size class and life stage of your species, plus the "5-minute rule" for portion size. It does not replace species-specific guidance from SeriouslyFish or your local fish store — it gives a defensible starting point.