Why winter is the risky season for a small aquatic frog
An African dwarf frog spends its whole life in the water, so it has no way to warm itself when the temperature around it falls — its body simply takes on the temperature of the tank. In summer that is rarely a problem, because most homes sit close to the warm range these frogs prefer. Winter changes the maths: heating cycles on and off, rooms cool sharply overnight, and a small tank loses heat far faster than a large one. A frog that was lively at teatime can be sitting in noticeably cooler water by morning, and repeated swings are harder on it than one steady, slightly cool reading.
Holding the water temperature steady
Start with the heater, because it is doing more work now than at any other time of year. Check that it is sized for the tank and still switching on reliably, and read a thermometer at the opposite end of the tank from the heater, so you see the coolest water the frog actually sits in rather than the warmest. Keep the tank away from exterior doors, single-glazed windows and radiators, all of which create local hot and cold spots. A snug lid matters more in winter than owners expect: it slows evaporation, keeps the air at the surface warm for the moments the frog rises to breathe, and cuts the chill from room draughts. When you change water, condition it and warm it to match the tank before it goes in — a bucket of cold water tipped straight in is the most common winter shock for these frogs.
Feeding and daily checks through the cold months
A cooler frog is a slower frog. Appetite often dips as the water cools, so offer the usual foods — small sinking pellets and thawed frozen bloodworms suit dwarf frogs well — in slightly smaller amounts, and lift out anything uneaten before it fouls the water. Watch that food actually reaches the frog: dwarf frogs find their meals largely by smell and are easily outcompeted by quicker tankmates, and in winter a shy frog may not bother competing at all. A two-minute daily look is worth more than any gadget — confirm the frog is swimming down comfortably, resting on the bottom rather than hanging at the surface, and rising to breathe in its normal unhurried way.
The winter signs that mean a vet
Most winter problems are gradual, which is exactly why they get missed. A frog that stops eating for several days running, floats at the surface and struggles to dive, or develops pale patches, redness or fuzzy growths on the skin needs an aquatic or exotics vet rather than another week of watching. So does a frog that becomes suddenly frantic or, at the other extreme, barely responds when the water beside it is gently disturbed. Note when you first saw the change and what the thermometer has been reading, because that history is genuinely useful to the vet. Keeping the daily temperature readings and feeding notes on KinsLe's Care Teams list gives everyone in the house the same picture, so a slow winter decline gets spotted while it is still easy to act on.