Reef Kalk 39 calculators
REEF KALK Chemistry and equipment arithmetic for reef aquaria. Everything runs in the browser, nothing is stored, no account. Each result writes itself into the address bar, so a link is a saved calculation. Every calculator shows its formula and its sources.
Find
Core chemistry — 6
01 ALKALINITY DOSING
How much carbonate to add to move dKH from where it is to where you want it. →
02 CALCIUM DOSING
Calcium chloride or a commercial calcium supplement, sized to a target in ppm. →
03 MAGNESIUM DOSING
Magnesium chloride, Epsom salt, or a blend of both, sized to a target in ppm. →
04 SALT MIX
Salt mass to bring RO/DI up to a target salinity, and what the mixed water should test at. →
05 SALINITY CONVERTER
Specific gravity, ppt, and conductivity, with the temperature correction that most conversion tables leave out. →
06 pH, ALKALINITY AND CO₂
Why pH sits where it does. Usually the answer is the air in the room, not the alkalinity. →
Dosing systems — 5
07 KALKWASSER
Limewater through the top off line, and the ceiling evaporation puts on how much alkalinity it can deliver. →
08 DAILY CONSUMPTION DOSING
Measure how fast the tank burns alkalinity, then size the daily dose that holds it flat. →
09 DOSER CALIBRATION
Turn a measured pump output into a schedule, and check what the tubing drift is costing you. →
10 ALK AND CALCIUM IMBALANCE
Alkalinity and calcium should track each other. When they do not, this says which one is actually wrong. →
11 CALCIUM REACTOR TUNING
Effluent drip rate to match your alkalinity demand, and what your current settings actually deliver. →
Nutrients — 5
12 RAISE NITRATE
Sodium or potassium nitrate to lift nitrate off the floor. Ultra low nutrient tanks starve corals and grow dinoflagellates. →
13 RAISE PHOSPHATE
Potassium phosphate to bring phosphate up off zero, in the very small quantities this actually needs. →
14 CARBON DOSING
Vodka, vinegar, or NoPox to drive nitrate and phosphate down, with the ramp schedule that keeps it safe. →
15 PHOSPHATE MEDIA
How much GFO to run for your volume, and when to change it. →
16 FEEDING AND NITRATE
How much nitrate and phosphate your feeding puts in each week. Usually the real answer to a nutrient problem. →
Treatment — 1
17 COPPER TREATMENT
Copper dose to reach a therapeutic level in a quarantine tank, from zero or from a measured reading. →
Maintenance — 5
18 ADJUST SALINITY
RO/DI to add to bring salinity down, or salt to add to bring it up, without shocking anything. →
19 WATER CHANGE
What a water change actually removes, how many it takes to reach a target, and what it does to alkalinity. →
20 EVAPORATION AND TOP OFF
How fast salinity climbs when top off stops, and how big an ATO reservoir needs to be. →
21 FIX A SALT BATCH
You mixed a batch and it came out wrong. How much more salt, or how much RO/DI, to land it on target. →
22 DRIP ACCLIMATION
Drip rate and time to bring shipping water up to tank parameters gently enough for inverts. →
Setup — 7
23 TANK VOLUME
Real water volume after sand, rock, and sump. Every dosing number on this site depends on getting this right. →
24 FISHLESS CYCLING
Ammonia dose to start a cycle, plus the nitrate and alkalinity that show up when it finishes. →
25 SAND AND ROCK QUANTITY
How much sand to buy for a bed depth, and how much rock a tank of this size takes. →
26 FILLED TANK WEIGHT
What the whole thing weighs once it is running, and what that works out to per square foot of floor. →
27 SUMP FLOOD CAPACITY
Whether the sump can hold what drains back when the power goes out. Test it before you find out the hard way. →
28 RO/DI OUTPUT
What your membrane actually produces at your water temperature and pressure, and how long the DI resin lasts. →
29 GLASS THICKNESS
Whether the glass on a tank is thick enough for the water height, using the standard bending stress method. →
Equipment — 8
30 RETURN PUMP HEAD LOSS
What flow you actually get at the top of the plumbing, not what the pump box claims at zero head. →
31 FLOW AND TURNOVER
Total in tank flow against what the corals you keep actually want. →
32 PAR AND DLI
Daily light integral from a PAR reading and a photoperiod, against what different corals want. →
33 HEATER SIZING
Watts to hold temperature against a cold room, and how long a given heater takes to recover. →
34 RUNNING COST
What the tank costs to run per month, added up across every piece of equipment. →
35 POWER FAILURE
How fast the tank cools with the heater off, and how long you have before it matters. →
36 OVERFLOW AND DRAIN
Whether the drain can carry the return pump, how deep the water runs over the weir, and whether the emergency line copes. →
37 UV STERILIZER
Flow rate through a UV for algae, bacteria, or parasites. The three targets need very different speeds. →
Reference — 2
38 UNIT CONVERTER
Alkalinity, nitrate, and phosphate units side by side. Two of these trip up almost everyone at least once. →
39 FREE AMMONIA
How much of a total ammonia reading is the toxic form. pH changes the answer by a factor of ten. →
READ FIRST Test your water before and after dosing. These numbers assume your test kit is accurate and your volume estimate is close, and both are often wrong. Dose into high flow away from corals, split large corrections across several days, and never chase a single test result.