Calculators

Reef Calculators

Below are some handy calculators to help you on your reefing journey.

Whilst we take every step to ensure accuracy, you should always check the calculations yourself and not rely on our mini apps as we cannot be liable for any mistakes in our calculators.

Salinity Calculator

Tool

Units

Volume (L)

Current salinity

Target salinity

Salt brand (only used when raising salinity)

Lowering assumes you remove saltwater and replace with RO/DI to keep final volume the same.

Nutrient Ratio Calculator

Compare nitrate and phosphate levels to assess balance and likely limitation.

Nitrate (NO₃) — ppm

Phosphate (PO₄) — ppm

This uses the nitrate-to-phosphate ratio as a **diagnostic hint**, not a rule.

Assessment

Many healthy reef tanks operate outside textbook ratios. Trends matter more than single numbers.

PAR Coverage Estimator

Multi-light PAR mapping for planning coverage and coral placement. Lights are automatically evenly spaced.

Tank length (cm)

Tank width (cm)

Tank depth (cm)

Mount height above water (cm)

Calibration factor

Number of lights

Top-down depth slice (cm from surface)

Calibration factor lets you match a PAR meter reading (e.g. set 1.10 if your real readings are ~10% higher).

This is an estimate. Real PAR depends on optics, mounting height, surface movement, and rock shading.

Ammonia Cycling Calculator

Work out how much ammonia to dose to reach a target concentration, and how much to redose after testing.

Tank volume (litres)

What are you doing?

Target ammonia (ppm as NH₃/NH₄⁺)

Ammonia product strength

Custom strength (mg/mL as NH₃-N)

This assumes your ammonia dosing product is expressed as mg/mL as NH₃-N (common for cycling calculators). If your bottle uses a different convention, use “Custom” and enter the correct strength.

Dose recommendation

Always dose slowly with circulation running. Retest after mixing.

If you’re fishless cycling, many hobbyists target around 1–2 ppm and redose only when it drops close to zero.

Medication & Quarantine Calculator

Enter treatment volume and generate a plan. Copper treatments require testing.

Treatment volume (litres)

Medication

Treatment option

Start date (optional)

Copper: test with a reliable kit/checker and increase slowly. Do not use copper with inverts/live rock/sand intended for reef use.

Always follow the product label. This tool is for planning and estimating only.

Substrate Calculator

Estimate substrate volume and weight from tank footprint and sandbed depth.

Units

Tank length (cm)

Tank width (cm)

Depth mode

Desired depth (cm)

Substrate type

Weight is an estimate — it varies by grain size, moisture, and brand.

Volume is calculated from tank length × width × average depth, then converted to litres. Weight uses the density preset you choose.

Should I Buy More Fish?

Answer the questions below to receive a scientifically-adjacent recommendation.

Tank size

Current stocking level

Age of the tank

Is your partner threatening to leave you?

Recommendation: Buy More Fish

Based on qualitative assessment, emotional wellbeing, and long-standing hobbyist precedent.