Great Aquariums Start Here
Live Chat Support
    Free Shipping On $175+
  • FREE Shipping On $175+
  • 14-Day Low Price Guarantee
  • 14-Day Low Price Guarantee
  • Same Day Shipping
  • Same Day Shipping
FREE Shipping on
Orders Over $175
Standard ground shipping (1-7 business days) starts at a low $5.99 and most orders over $175 ship FREE. Learn More
If you find a product we sell for a lower price at another online store, we will match their price—today and up to 14 days after you've purchased the item! Learn More
Same Day Shipping
We promise to ship your order as fast as humanly possible. In fact, 99% of orders placed before 6 pm EST ship the same day! Learn More

Aquarium Thermometers & Fish Tank Thermometers, Refractometers & Hydrometers

American Marine Pinpoint Wireless Aquarium Thermometer System
Digital read out of aquarium temperatures. One monitor can read up to 4 separate readings by utilizing additional sensors.
Coralife Digital Thermometer
Readings in 0.1 degrees Fahrenheit or Celsius. Temperature range -10 degrees F to 140 degrees F (-23 degrees C to 60 degrees C).
Hagen Floating, Standing, Stainless, Aquarius & Nova Thermometers
A wide variety of thermometers to choose from. Inexpensive, accurate and easy to read.
Hydra Aquatics Thermometers
Designed to hang on to the walls of rimless glass tanks 3-8mm thick. Reliable, easy to read and measure temperatures ranging 30-100 degress Fahrenheit. The minimal design allows aquarium keepers to place the thermometers inside their tanks without obstructing views.
JBJ Digi-Temp Thermometer
Digi-Temp is perfect for Nano Cubes that demands compact size with pinpoint accuracy.
Lifegard Aquatics Digital Thermometers
Little Time & Temp Digital clock/thermometer with light & the Big Digital Temp Alert Thermometer with large face digital thermometer with alert features.
Refractometers / Hydrometer
American Marine PinPoint Electronic Salinity Monitor
PINPOINT Salinity Monitor™ will accurately and immediately measure the amount of salt in any marine or freshwater system. The accuracy is superb!
Coralife Deep Six Hydrometer
The unique design allows hobbyists to take water samples at six inches in depth without submerging their hands in the water, thus avoiding the possibility of contamination.
Hagen Hydrometer
Accurate and easy to read floating hydrometer and thermometer all in one.
Hanna Instruments Digital Seawater Refractometer
A rugged portable, water resistant device that utilizes the measurement of the refractive index to determine the salinity of natural and artificial seawater, ocean water or brackish intermediates.
Milwaukee Seawater Digital Refractometer
Simple and easy to use! Samples are measured after a simple user calibration with distilled or deionized water. Within seconds, the refractive index and temperature are measured. Temperature is also displayed on the large dual-level display.
Red Sea Hydrometer with Digital Thermometer
Unique intergrated hydrometer and thermometer. Patented design enables device to be permanently installed inside aquarium, allowing time for micro bubbles to dissolve for continuous, accurate, real-time reading of salinity in addition to regular periodic reading.
The most accurate way to test your aquariums' specific gravity. An absolute must for the marine hobbyist, we offer 4 different models so you can choose the right model at the right cost.
SeaTest Hydrometer
Improved design delivers precise salinity and specific gravity readings. Easy-fill keep hands dry when filling. Durable and easy-read 2-color scale and an extra-wide base.
Salinity is a measure of the concentration of dissolved salts in water. Normal seawater tends to run in the range of 1.021 to 1.025 with the Red Sea area having a slightly higher level of up to 1.027. Salinity can be measured in a marine or reef aquarium a hydrometer or refractometer.

Hydrometers are easy-to-use devices that give readings in specific gravity and/or salinity. It is recommended that you first calibrate a hydrometer with a refractometer or salinity monitor before usage. Refractometers are much more accurate and are also very easy-to-use.

Fish tank or aquarium thermometers are an extremely important item for any aquatic habitat. Monitoring temperatures for better control and stability will aid in the overall health of your animals. There are many different types of thermometers to choose from, including digital (battery operated), glass and liquid crystal stick-on.

This item is temporarily unavailable but will be back in stock soon.

Item #
Click the Add To Cart button below if you'd like to reserve this item today. Any other items included in your order will be immediately processed and shipped. We will ship this item separately as soon as it arrives. We will not charge you for this item until it ships and you will incur no additional shipping charges.

Enter your email address in the field below and click the Notify Me button if you'd like us to send you an email when this item becomes available. Although you will be immediately notified when we have stock on hand, we will not reserve any units for you; you must return to our website and place an order.

Your Email:
Just enter your email address below and we'll let you know when the product you are looking for becomes available!

Item Code:
Your Email:
Email Specials
Subscribe to our newsletter feed.
Newsletter Tips & Tricks! New Products!
Discounts & Promos!
April 6, 2015
"They have things that no one has and they show you how to use it."

April 3, 2015
"I wish I would have found your website sooner. Now I’m telling everyone I know about it."

April 1, 2015
"Best prices and products. I absolutely love Marine Depot!"

Win a $100 Gift Card Sign up to get our best deals, expert tips and a chance to win $100 to spend at Marine Depot!