Hydor ETH In-Line Heaters

The first compact aquarium heater that operates externally, saving interior aquarium space. Installs vertically in the return line of a canister filter or sump, allowing better heat distribution as water returns to the aquarium. Built-in clamps for easy plumbing, and temperature adjusts from 65-93°F on an ergonomic knob. Durable, plastic casing protects internal parts. Indicator lights up when heating. 5-1/2 ft cord. UL-Listed.

Please click on "More Information" for additional features and installation instructions.

Patented Heating Technology
The ETH In-Line Heater uses PTC, a heating technology patented by Hydor. Its heating element is made of a special polymer that has been silk printed with special ink. The ink heats up with the passing of electric current, and the heat is then transferred to the water. There's no danger of damage to equipment if unit is left running without water flow for a short period of time. Heater switches "Off" to avoid overheating.

Installation Instructions:
Install by cutting the outlet tube of the external filter, and by connecting the two parts of the tube onto both sides of the heater. If the external filter is already installed, it is important to shut off the valve taps and empty out all the water before cutting the outlet tubing. When finished, reactivate the aquarium's water circulation and connect the heater into the power source. After the first 24 hours of operation, we recommend that you check to make sure all connections are tight and leak-free.

Safety Precautions:

1. Unplug all electrical appliances before making water changes or performing any maintenance.
2. Use this heater indoors only.
3. Check voltage to verify that the voltage reported on the heater label corresponds to your electrical supply.
4. DO NOT use if either the cable or the heater are damaged.
5. This device is not submersible (for in-line use only).
6. DO NOT immerse unit when cleaning.
7. DO NOT disassemble unit when cleaning.

Kurt L
Glenview, IL

I was and am disappointed by my in-tank heaters. They can swing 3 degrees up or down from where I want a stable temp. The Hydor ETH is great. Holds a very stable temperature in my 46 gal. No unsightly heater in the tank. Unit is somewhat large. The only potential issue I see is the temperature control dial could get bumped and move position. A cover over the dial would make this unit 10 out of 10 stars instead of 9 out of 10. A minor gripe for an excellent product.

James J
Davenport, IA

It is the best heater I have ever had; it works to .5 of a degree. But it is about a foot long and is close to the size of a soda can around a bit smaller. So with it behind the tank is can be a tight fit if your stand is low to the ground. I LOVE MINE!!

Nick A
San Bernardino, CA

This is the greatest heater for aquariums up to 70 gallons - no visible wires and a constant temperature is always kept. I recommend it to everyone.

Arik A
Rochester, NY

WORTH EVERY PENNY!!!! I've been using this for a couple of weeks, and I have yet to see the temperature of my tank deviate from 76 degrees (measured with 3 thermometers in various positions of the tank!). Not to mention the primary benefit, less clutter in the tank. You'll never go back to traditional heaters again!!!

Robby R
Springfield, MO

This heater has several advantages: it saves space in the tank, saves the heater from aggresive fish, promotes better temperature distrobution, and it is very accurate. I have had mine for a few months now and the temperature has never moved from where I left it. This is a great product!

Curt T
Barrington, IL

This is the best heater I have ever had. I got the 200W with 5/8 connection to use in a 40gal tank. The tank is for my turtle so it's filled w/ 30gal only. It's in the office where ambient temperature varies from 60 to 82 degrees, especially on weekends. I used a thermometer with max/min and the heater keeps the temperature within +/- 0.3 of the set point, which is the best I have ever seen.

Sabrina R
Pearland, TX

This heater is GREAT. I was a little nervious about leaks but it works really well and heats the water perfectly.

Mark S
Superior, WI

I have a freshwater 125 gal setup and got by for a year on one 300w unit. My house winter temp is 64 deg F and this heater would hold my temp of 78.5 all winter. I now have 2 of these side by side and temp matched just for peace of mind. These are the best heaters I have tried and hold temp exactly where you put it and you do not have to look at an ugly heater and cord.

Dianne R
Ithaca, MI

Such accuracy - Installed this heater and the temp is ROCK SOLID - right on the dot - hasn't wavered more than .5 degrees. It is so comforting to know the temp is exactly what you set the thermostat for.:) It is worth the extra cost-no doubt.

S. Wong
Aliso Viejo, CA

This is a great heater if you don't want a ugly heater in your tank. It holds a very stable temperature. The heater is bigger then the pictures would indicate, but fits nicely behind the tank. It is not to heavy to just hang from the outlet hose. There is an indicator light to show that the heater is heating.