Collection: Thermometers

What the Water Is Actually Doing

A heater dial reports what the heater intends. A thermometer reports what the water is at, and those two disagree more often than people expect. It is the cheapest instrument in the tank and usually the first thing to show a heater going wrong.

Types Here

• Floating thermometers — low-cost analog units, some with a suction cup to hold position.
• Submersible digital thermometers — probe in the water, display outside.
• External digital thermometers — mount on the outside of the aquarium, nothing in the water.

Run two. Cross-checking a pair is the only reliable way to catch one drifting, and a stuck reading looks exactly like a stable tank right up until something dies. Take readings away from the heater and the return flow so the number reflects the tank rather than its warmest corner. Questions? Email info@jlaquatics.com. Ships across the US and Canada.