The core readings every log needs
For a tank holding nerite snails, each entry in your log should carry the date and six routine results: ammonia, nitrite, nitrate, pH, temperature, and the two hardness measures, general hardness and carbonate hardness. Ammonia and nitrite should read zero in a settled tank, and logging them anyway is what proves the tank is settled rather than merely assumed so. Nitrate is the slow mover worth trending - it creeps between water changes and tells you whether your change schedule is keeping up. Temperature looks boring until a heater drifts, and the log is how you notice it drifted last month, not today.
Hardness and pH: the shell's building budget
For a snail, two of those numbers outrank the rest. A nerite builds and maintains its shell from minerals in the water, so it needs alkaline conditions - a pH comfortably above 7 - backed by genuine hardness, not acidity softened on paper. In soft or acidic water the shell quietly dissolves faster than the snail can repair it, showing up as pitting, thinning and a pale, chalky surface, worst on the oldest growth near the shell's tip. Log general and carbonate hardness beside every pH reading: a pH figure on its own cannot tell you whether the water can actually support a shell, and the pair together can.
Copper: the occasional reading that must be zero
The seventh result belongs in the log on specific occasions rather than weekly: copper, checked whenever anything new is about to enter the water. Copper-based fish treatments, some algae products and some plant fertilisers can carry copper into a tank, and snails, as invertebrates, are far more sensitive to it than fish - a level the fish shrug off can kill a nerite. A log entry that simply records 'copper tested before treatment, read zero' is cheap insurance, and noting which products you have used in the tank tells a future you exactly what to suspect if a snail ever stops moving.
Log the action, not just the number
A column of numbers with no decisions attached is data you will never use. Beside each set of results, write what you did: water changed, filter rinsed, feeding reduced, nothing - tank stable. Note the snail-side observations too: grazing normally, new shell growth smooth, an old erosion mark unchanged. Those pairings are what turn the log into a diagnostic tool, because when something does shift, you can read backwards to the week the hardness slipped or the nitrate trend turned, instead of guessing which of six variables moved first.
Keep the record with the tank's story
Test kits come and go, but the log only works if it survives in one place and stays attached to the tank it describes - including through a house move, a tank upgrade or a sitter's weekend in charge. Keeping the nerite tank's results, set-up details and product history together in its Pet Passport on KinsLe means the record travels as one packet: anyone taking over the tank inherits the trends, the safe products and the shell-health history, not just a bottle of test strips and good intentions.