The Imagitarium Aquarium Strip Thermometer is a liquid crystal thermometer that sticks to the outside of your aquarium glass and displays water temperature through the glass wall without any part of the thermometer entering the water. You press it onto the exterior glass below the waterline, and the liquid crystal cells change color at different temperatures, showing you a reading in Fahrenheit and Celsius. It's the Petco house brand version of the very common adhesive strip thermometer style that has been in the hobby for decades.
It works, but its accuracy is limited. Liquid crystal strip thermometers typically read within 2-3°F of actual water temperature under normal conditions, and they're affected by room temperature, direct sunlight, and the proximity of tank lighting. For casual monitoring where you want to confirm your heater is doing something, they're fine. For precise temperature control with sensitive livestock, you need a digital thermometer to verify. This guide covers how to get the most accurate reading from a strip thermometer, how it compares to other thermometer types, and when it's worth upgrading.
How Liquid Crystal Strip Thermometers Work
The strip contains a series of cholesteric liquid crystal (CLC) cells, each calibrated to change color at a specific temperature. When a cell reaches its activation temperature, it reflects light in the visible spectrum, showing a color. The cell at the current temperature appears bright green or teal; cells above or below appear orange or red (or are inactive).
This technology is reliable within a range but has inherent limitations:
- The cells activate based on the temperature of the glass surface they're adhered to, not directly on water temperature
- Glass acts as a minor thermal insulator, so the strip reads slightly below actual water temperature in most conditions
- Ambient air temperature affects the reading: if the room is 65°F and your tank is 78°F, the outside surface of the glass reads somewhere between those two values
- Most strips have a resolution of 1-2°F, so you can't detect 0.5°F variations
In controlled testing by hobbyists who compared strip thermometers to calibrated digital probes, strip thermometers typically read 1-3°F below actual water temperature in normally heated home environments.
How to Get the Most Accurate Reading
Placement Matters
Attach the strip on the front or side glass, below the waterline by at least 2 inches, and away from direct light. Placing it directly under a light panel causes the strip to read high because the light heats the glass surface independently of the water temperature.
Keep it away from the heater side of the tank. The glass immediately adjacent to a heater reads higher than the average tank temperature, since the heater creates a localized temperature plume.
The best position is on the front glass, lower third of the tank, roughly in the middle of the front panel horizontally.
Reading Technique
The active color is bright teal or green. Adjacent cells may show a faint orange color. Read the temperature at the center of the bright cell, not the faint adjacent ones. If two cells appear equally bright, the actual temperature is between the two displayed values.
Under artificial lighting or at certain angles, the color can be hard to distinguish. View the strip from straight-on rather than at an angle, and in ambient room lighting rather than the aquarium's own lighting, if possible.
Accuracy Compared to Other Thermometer Types
Digital Submersible Thermometers
The Zoo Med TH-22 Economy Digital Aquarium Thermometer uses a probe inserted into the water attached to a LCD display that sits on the tank rim. It reads to 0.1°F and is accurate to within 0.5°F with a fresh battery. Cost is about $6-10.
The Marina Digital Thermometer (similar design, about $8-12) and the INKBIRD Aquarium Thermometer ($12-15) are comparable options. Digital probes measure actual water temperature directly and are not affected by ambient air temperature or glass thermal insulation.
For most home aquariums, a digital thermometer is the minimum I'd recommend if you're keeping fish with specific temperature requirements.
Floating Glass Thermometers
Traditional glass column thermometers float inside the tank. The Marina floating thermometer and similar models read to 0.5-1°F increments. They're more accurate than strip thermometers but require physical access inside the tank to read and can break, releasing mercury (in older models) or alcohol into the water. Modern floating thermometers use alcohol or red dye with no mercury risk.
Infrared Thermometers
Infrared (non-contact) thermometers like the Etekcity Lasergrip 1080 read surface temperature. They can be used on the glass exterior for a quick reading, but like the strip thermometer, they measure glass surface temperature rather than water temperature. Useful for a quick check but not for precise monitoring.
Electronic Aquarium Controllers
For tanks where temperature stability is critical (reef tanks, discus tanks, breeding setups), electronic controllers like the InkBird ITC-306 or the Ranco ETC-111000 have probes submersed directly in the water and control heater and chiller outlets based on the reading. These are accurate to 0.1°F and provide alerts for out-of-range conditions.
When a Strip Thermometer Is (and Isn't) Enough
Good Use Cases
- Secondary visual check alongside a digital thermometer
- Tanks with hardy fish (bettas, goldfish, danios) where +/- 2°F accuracy is acceptable
- Budget setups where you want some temperature indication without additional cost
- Quick visual confirmation during water changes
The Imagitarium strip thermometer (and equivalent options from Marina, Penn-Plax, and Tetra) runs $2-5, making it an inexpensive supplemental tool.
When You Need More Precision
- Discus fish: require stable 82-86°F; outside that range health degrades quickly
- Saltwater reef tanks with SPS coral: temperature swings of more than 2°F cause bleaching
- Freshwater breeding: specific temperature triggers spawning; need control to within 1°F
- Cold water tanks: maintaining a species at 62-65°F requires knowing if you've hit 67°F
- Any time you're treating disease: some medications have reduced efficacy at incorrect temperatures
In these cases, use a digital probe thermometer as your primary instrument. You can still keep the strip thermometer as a backup visual indicator.
Installing the Imagitarium Strip Thermometer
The strip comes with an adhesive backing. Clean the exterior glass with isopropyl alcohol and let it dry fully before attaching. Press the strip firmly and hold for 30 seconds. If the glass has any residue (algae cleaner, fingerprints, water spots), the adhesive won't bond properly and the strip will eventually peel.
If the strip peels off after a few months, the adhesive has dried out. Some aquarists re-secure their strip with a piece of clear packing tape over the top of the strip. This holds it in place and doesn't affect readability.
For a broader look at all the monitoring and measurement tools worth having, our guide to Best Aquarium Equipment covers options across price ranges.
FAQ
How accurate is the Imagitarium strip thermometer?
Within 2-3°F of actual water temperature under typical home conditions. The main source of inaccuracy is that the strip reads glass surface temperature, which is affected by ambient room air temperature. In a 70°F room with a tank at 78°F, the glass might read 75-76°F. Strips also have low resolution, usually 1-2°F per marked increment.
Why does my strip thermometer show two temperatures at once?
You're seeing two adjacent cells that are near the transition point. The actual temperature is between the two active readings. For example, if the 76°F and 78°F cells are both faintly active, your water is approximately 77°F. Strip thermometers with 2°F increments between markings always have this ambiguity near transition temperatures.
Can I use a strip thermometer on an acrylic tank?
Yes, but be careful with the adhesive. Some acrylic formulations are sensitive to adhesive removers. If you ever need to remove the strip, use a plastic scraper (not metal) and avoid acetone or alcohol-based solvents. Goo Gone works on most acrylics without damaging the material.
My strip thermometer reads 10°F lower than my digital thermometer. Is the strip defective?
A 10°F difference suggests a defect or the strip has been exposed to a temperature outside its rated range (usually 64-86°F). Strip thermometer cells can be permanently damaged by temperature extremes. If the strip reading is far off from your digital probe, replace the strip. They cost $2-5 and aren't worth troubleshooting extensively.