Prepare everything before you leave, and let the sitter's job be using what you prepared. Evaporation in a small tank during a heatwave is fast and unforgiving: the volume is small, so the level drops visibly between visits, and the salts and waste left behind concentrate in what remains. Topping up is the right response, but only topping up done your way — with water you conditioned in advance, to a line you marked, against a temperature limit you wrote down. A sitter handed improvisation instead of preparation will improvise, and warm fish pay for guesses.
Prepare the Water, the Line and the Card
Fill a clean container with conditioned top-up water — tap water treated with conditioner and left standing beside the tank, so it sits at room temperature close to the tank's warmth — and label it plainly as top-up water. For an absence of more than a couple of days in serious heat, prepare a second labelled container in the same way, since running out invites the tap-water shortcut the setup exists to prevent. Mark the fill line on the glass at the tank's normal level with a clear line, and place the thermometer where it can be read without opening anything or moving the lid. The written card ties the three together: it names the container, the line and the thermometer, and gives the visit order below.
The Sitter's Visit, in Order
First, read the thermometer and compare it with the threshold written on the card. If the reading has passed that threshold, the visit changes: the sitter phones you before adding anything, and follows your instructions on the call rather than improvising at the glass. If the reading sits below the threshold, check the level against the marked line, then add the prepared water slowly, in small amounts, pausing between pours, until the surface reaches the line and no higher — overfilling a small tank in heat trades one stress for another and can defeat the lid and filter arrangement. Use only the labelled container, even if it means a level left slightly low when the prepared water runs unexpectedly short, and note on the card what was added and what the thermometer read, so the next visit starts informed.
What the Sitter Must Never Improvise
Write the prohibitions on the card as plainly as the steps, since heat makes clever ideas tempting. No ice: dropping ice into a small warm tank chills the water unevenly and fast, shocking the very fish it was meant to rescue, and melting ice of unknown source adds water you never conditioned. No cold water from the tap or from cold storage, however clean it looks, for the same reason — temperature shock harms sooner than a low level does. No extra food to make up for a short visit, no unplugging or adjusting equipment to cool the tank, and no moving the tank into a cooler spot, which risks the glass, the stand and the fish in one lift. Every temptation on that list is replaced by one action: phone you.
Visits, Thresholds and Small Volumes
Set the phone threshold on the card as a written number a couple of degrees above the tank's usual reading — a limit you choose from your own tank's normal range, not a figure borrowed from another setup — so the sitter judges a number, not a feeling. In a heatwave, plan daily visits for a small tank even if the fish could be fed less often, since the top-up, not the food, is the visit's purpose, and a day skipped in heat shows in both level and temperature. Tell the sitter the absence length and the visit rhythm on the card as well, and keep your phone reachable for the threshold call you have asked them to make. Shared ahead of the trip, that same card sits neatly inside the temporary access KinsLe provides through Care Pass, where the sitter can re-read the line, the threshold and the container label wording whenever they need it.