Saving is optional and stores this plan in this browser until you remove it.
Changing units reinterprets the entered volume; enter the number in your selected unit. No brand presets are provided. Enter the salt mass per litre documented for your chosen target salinity, or a ratio you have verified yourself. Target salinity is recorded, not used to invent a mixing ratio.
Net system volume: enter a value greater than zero.
Annual costs use 365 ÷ interval; fractional batches describe an annualised budget, not a calendar schedule. No evaporation top-up, waste, energy, delivery, additional additives or equipment costs are included. Use the ownership calculator to add these separately. Formula mixing-1.0.
Import saved salt and water costs into your ownership plan →
What to check before calculating
Use net system water volume after displacement. Obtain grams of salt per litre at your chosen target from the product’s current manufacturer instructions or your own verified mixing process. Brands and products differ. We have not reviewed brand presets for this tool, so none are supplied. Target salinity alone cannot determine the correct mass of every salt blend.
Show the workings
Batch litres = net litres × change percentage ÷ 100. Salt kg = batch litres × g/L ÷ 1,000. Salt cost = salt kg × pack price ÷ pack kg. Annualised batches = 365 ÷ interval in days. Annual water cost = batch litres × annualised batches × water price per litre. One US gallon = 3.785411784 litres; one imperial gallon = 4.54609 litres.
Arithmetic example — not a mixing recommendation
Using a synthetic 35 g/L test ratio: a 200-litre system, 10% change every seven days and a 20 kg pack costing £60 gives 20 litres and 0.7 kg per batch, £2.10 salt per batch, 36.5 kg salt/year and £109.50 annual salt cost. Do not use this synthetic ratio for your aquarium without checking your product and measuring salinity.
Common questions
Does the calculator choose a safe schedule?
No. You supply frequency and volume according to your system and appropriate husbandry guidance.
Why are annual batches fractional?
They represent 365 days divided by the interval for comparable budgeting. An actual calendar’s number of changes depends on start dates.
Can I use this for evaporation top-up?
No. Evaporation top-up and replacing removed saltwater are different tasks. Follow appropriate product and aquarium guidance.
Complete your plan
Read reef salt mixing costs and saltwater preparation guidance. Add the annual salt and water totals once in the ownership calculator, replacing corresponding estimates to avoid double-counting.