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Free reef tools
Reef & Aquarium Calculators
Nineteen free calculators for saltwater and reef tanks: volume, salt, dosing for popular brands, flow, media and running costs. Built by the Frags2Fishes service team from the numbers we use on client tanks every week.
Free, no sign-up, and every one works on your phone.
Tank setup
Size, weight, rock and equipmentTank Water Volume
Gallons for 9 tank shapes, with your real water level.
Open calculator →Total System Volume
Display plus sump and refugium, minus rock and sand.
Open calculator →Tank Weight & Floor Load
Glass, water, rock and sand, and pounds per square foot.
Open calculator →Sand Bed
Pounds of sand for the depth you want.
Open calculator →Rock
How much rock for an open, medium or full scape.
Open calculator →Heater Size
Watts you need, split into two heaters.
Open calculator →Return Pump & Flow
Pump flow at your head height, plus powerhead flow.
Open calculator →Water chemistry
Salt, salinity and supplementsSalt Mix
How much salt to mix, or top up, to your target salinity.
Open calculator →Salinity Adjust
How much water to swap to raise or lower salinity.
Open calculator →Unit Converter
SG and ppt, dKH and meq/L, phosphate, nitrate, °F and °C.
Open calculator →Seawater Properties
Density and specific gravity at any temperature.
Open calculator →Alkalinity Dosing
How much to dose, and how to split it safely.
Open calculator →Calcium Dosing
Calcium chloride amounts and a safe daily plan.
Open calculator →Magnesium Dosing
Magnesium chloride and sulfate, with a split plan.
Open calculator →Upkeep
Water changes, media and running costsWater Change Planner
What your schedule actually removes, and the salt it uses.
Open calculator →GFO (Phosphate Media)
Starting amount of GFO for your system.
Open calculator →Activated Carbon
Carbon for clear water and fewer toxins.
Open calculator →RO/DI Output
Real gallons per day for your water pressure and temperature.
Open calculator →Electric Bill
What your tank costs to run each month.
Open calculator →No calculator matches that. Try "salt", "volume" or "dosing".
Calculators
Common questions
Which volume should I use for dosing?
Your total system volume: display plus sump and refugium, minus what rock and sand displace. The Total System Volume calculator works it out, and “Use as my tank” carries it into every other calculator.
Are these numbers exact?
They are the formulas our service techs use, but test kits, salt brands and rock all vary. Dose in steps, test, and adjust. Anything that could hurt livestock shows a safe daily limit.
Where do the product dosing strengths come from?
From each maker’s label directions. A few products marked “our figure” (DIY powders, BRS Pharma mixes, kalkwasser, All-For-Reef) are worked out from the recipe or the published concentration. If your bottle says something different, follow the bottle.
Do the calculators work in metric?
Yes. Switch to Metric on any calculator and every field and result changes to centimetres, litres, kilograms and degrees Celsius.
Rather have us dial it in?
Frags2Fishes service techs test, dose and maintain reef tanks across PA, MD, DE, NJ and VA, and beyond.
