A sitter standing in front of a tank cannot judge a test result without knowing what healthy looks like in your tank. Your job before a holiday is to capture that healthy picture while everything is normal, in your own kit's readings, so any later test has something real to be compared against.
The Baseline Set to Record
Test the tank shortly before leaving, on a settled day when the fish are feeding and behaving normally, and record the baseline set in full: ammonia, nitrite, nitrate, pH, and temperature.
Write the values exactly as your kit shows them. These are your tank's values from your kit, not universal target numbers copied from elsewhere, because kits differ, tanks differ, and a sitter comparing two readings from the same kit learns more than a sitter comparing your fish to a generic chart. If you test more than once in the final days, label the most recent healthy test clearly as the baseline the sitter should use.
Take the baseline after your normal maintenance rhythm, not immediately after an unusually large water change or a deep clean that makes the tank look temporarily different from its everyday state. The point is an ordinary, healthy day.
The Equipment State Beside the Readings
Note the equipment state on the same sheet: filter running, heater steady, and anything else the sitter should expect to see, hear, or feel. Describe the normal signs plainly, such as water moving at the filter outlet, the heater light cycling as it usually does, and the tank holding its usual temperature through the day.
Equipment silence is often the first real warning while you are away. A filter that has stopped, a heater that has failed, or a temperature that has drifted away from the baseline explains a changed reading faster than the reading alone, and it tells the sitter whether the first call is about water or about hardware.
Also note what you last did and when: the last water change, the last filter rinse or media check, and the feeding amount the sitter should match. Overfeeding by a kind sitter is a common holiday problem, and a written amount prevents the slow water-quality slide that follows generous handfuls.
What Counts as Off, and Who to Call
Write what counts as off in plain language tied to your baseline. A reading clearly unlike the baseline, a temperature moved away from its usual figure, equipment stopped or noisy in a new way, cloudy water that was clear at baseline, or fish gasping, hiding, or refusing food all count as off and should trigger a call rather than quiet watching.
Name who to call first, with the number on the same sheet: you, then a knowledgeable backup if you are unreachable, then your aquatic store or veterinarian as you direct. Say what the sitter may do while waiting for advice, such as stopping feeding and leaving equipment settings alone unless you tell them otherwise, so a helpful person does not make several changes at once and hide the cause.
Leave the test kit, the baseline sheet, the spare batteries or chargers for equipment, and the contact list together beside the tank, and show the sitter where they are before you go. A baseline buried in a drawer at the other end of the house will not be found during a worried midnight test.
KinsLe's Pet Passport page stores equipment notes beside baseline values, so whoever feeds the fish knows precisely what normal looked like.