Aquarium Thermometer

Temperature is one of the most critical parameters in an aquarium. Fish, shrimp, and plants all have specific temperature ranges for optimal health, and even small deviations can cause stress, disease, or death. An accurate, reliable thermometer is the only way to monitor this parameter continuously.

Types of Aquarium Thermometers

Glass (Alcohol/Mercury-Free)

The traditional choice. A glass tube with a coloured alcohol column floats inside the tank via a suction cup. Affordable and always-on, but can be difficult to read and will shatter if dropped.

Digital Stick-On (LCD Strip)

A thin adhesive strip applied to the outside of the glass. Uses liquid crystal technology that changes colour with temperature. Very affordable and unobtrusive, but only accurate to ±1–2°C and reads the glass temperature, not the water directly.

Digital Probe

A battery-powered LCD display unit (mounted outside the tank) connected to a thin probe submerged in the water. Highly accurate (±0.1°C on premium models), easy to read, and some models include high/low temperature alerts.

Inline

Installed on canister filter tubing externally. Reads the water temperature as it flows through the return line. No equipment visible inside the tank. Premium option for clean aquascapes.

Which Thermometer Should You Choose?

| Type | Accuracy | Visibility | Price | Best For | |---|---|---|---|---| | Glass | ±0.5°C | In-tank | $3–8 | Budget, always-visible reading | | LCD Strip | ±1–2°C | Outside glass | $2–5 | Quick reference, nano tanks | | Digital Probe | ±0.1°C | Probe in-tank, display outside | $10–25 | Precision, alerts | | Inline | ±0.5°C | External only | $15–30 | Clean scapes, canister users |

Ideal Temperature Ranges

| Livestock | Range | |---|---| | Tropical Fish (general) | 24–27°C (75–80°F) | | Discus | 28–30°C (82–86°F) | | Neocaridina Shrimp | 20–26°C (68–78°F) | | Caridina Shrimp | 20–24°C (68–75°F) | | Cold Water / White Cloud Minnows | 16–22°C (60–72°F) |

Placement Tips

• Avoid heater proximity: Place the thermometer away from the heater to get a true reading of the ambient water temperature.
• Mid-depth: Position at mid-water depth for the most representative reading.
• Flow area: Place in an area with water flow so the reading reflects the circulated temperature.

Trusted Brands

• JBL: Excellent digital probe thermometers with alerts.
• Fluval: Reliable glass and digital options.
• Inkbird: Precision digital controllers with probes (also function as thermostats).
• Marina: Budget glass thermometers, widely available.

Pros & Cons

Advantages

• Essential monitoring: The only way to know your exact water temperature.
• Affordable: Even premium digital models are under $25.
• Early warning: Detect heater malfunctions or chiller failures before they harm livestock.
• Simple: No setup or calibration required for most models.

Considerations

• Glass breakage: Glass thermometers can shatter in the tank.
• Battery life: Digital models require periodic battery replacement.
• LCD strip limitations: Stick-on strips are the least accurate option.
• Placement matters: Incorrect placement near heaters gives misleading readings.