Hydor Hydor ETH External Thermal Heater - In Line Heater Aquarium Heaters at Linens 'n Things

On March 24, 2013:
I have a 300 watt on the return line on my 80 and a 200 watt on my 37 gal reef. Both heaters work flawlessly and keep the clutter our of the tank or sump.

On March 9, 2013:
What more is there? It is easily hidden, and it maintains steady water temps. Easily some of the best money spent on this hobby.

On December 27, 2012:
If you use canister filters, stop reading this review and ORDER this heater. You will be amazed at how easy it is to install and how GREAT it is when you don't have to look at ugly submersible heaters. I removed FOUR submersibles from my 125 gallon tank and installed two of the 300 watt models and they immediately got my temp up to the desired level and is keeping it there. I wish I had known about these sooner and I believe they are the only heater that anyone with a canister filter should consider.

On October 30, 2012:
Arrived quickly and in great conditions. Set up and running for about a week now with no issues and constantly keeps temp in check. Best heater I've used as water is forced passed the heating element to constantly regulate and measure temp.

On September 16, 2012:
I've had this heater for over a year and it works great. Fit perfect with my magnum350. Even temp all the time.

On May 23, 2012:
I love this inline heater. No leaks at all in the connections. It is keeping the water at the right temp, and best of all, it is not in the tank.

On May 27, 2011:
Accurate temperature control and eliminates the use of an in tank heater. It was simple to install as well. My only real complaints are it does not come with a hanger and the control knob is too easy to turn... meaning it is easy to bump the temp out of place. Also Pet Mountain has the best price on the net for this model! If you need a reliable heater and love the idea of an external unit, this is your heater.

On April 12, 2011:
So far these heaters seem great. They do fit my canister hoses perfectly, Rena xp3 with 5/8" hoses. I've read other reviews stating fit problems so I have to imagine that these were with the other model that does state 1/2" Anyway, these are great for additional heating without cluttering up the tank. Now hopefully they'll do the job for at least several years....

On November 2, 2010:
This thing advertises as being for external canister filters, but like others have said, the fittings are too small. There are lots of methods they could use to improve the fitting connections. Disappointing that they didn't bother.

On October 27, 2010:
I received this yesterday & tried to attach it to my Rena XP3 last night. Like others have said, the fitting is to small for the tubes on the canister filter. I used metal hose clamps and will see if that will hold. Seems like they should really rethink the connection method to make it more user friendly. Pet Mountain has great prices but their "saver shipping" is slow. Took 8 calendar days from CA to TX.

On October 17, 2010:
i bought 1 for my 55 g tank and am going to get 2 more for my other tanks

On October 12, 2010:
This is a great heater but it really cuts down on the water flow on my Fluval 405.

On September 29, 2010:
The ETH External Thermal Heater is perfect. The temperature stays exactly where the dial is set. No crazy up and down swings. I replaced my two submersible heaters with this in-line heater. It was easy to install, and let's just say I am not the most "handy" person in the world when it comes to installation. I would recommend this heater to anyone with out reservation.

On September 11, 2010:
I have had many aquariums and lots of hard equipment. So far, the Hydor ETH-300 inline heater is by FAR the best I have owned. Being out of the tank, there are no worries of fish getting burnt, or glass shattering in the tank, and the heat is spread through the tank by the current of the return, ensuring there are no hotspots near the heater. Highly recommend!

On August 5, 2010:
Packed nicely and delivered on time. Thank you.

On May 22, 2010:
The heater works great and keeps consistent temperatures. My only problem with it was connecting it to the outlet hose from the filter to the tank. The outlet hose on my Fluval FX5 is 3/4" inside diameter, this heater uses a 5/8" inside diameter hose. I used a 5/8" (ID) plastic hose, a 3/4" to 5/8" reduction connector and some clamps to make it fit. I'm still concerned about the reduction in water flow because of the smaller diameter heater.

On February 26, 2010:
Great heater - temp doesn't fluctuate much and best price around ($45 with free shipping). But, I spent few days and few trips to hardware stores to make it fit with Eheim 2213 canister filter. This unit has 5/8" internal dimension for input and output outlet. My Eheim 2213 has 1/2" internal dimension pipes. I had to buy 1 ft of 5/8" pipe, 2 pieces of 5/8" to 1/2" plastic reducer (or coupling) and 6 clamps to tighten things up. Then it worked. I wish they make these heaters with different outlet sizes.

On January 20, 2010:
I read good reviews on this item. I have a 125 gallon tank, and even though the inline heater is rated up to 90 gallons, it heated my water up to 78 degrees in less than 5 hours, and has kept it there. No unsightly heater in my tank. Simply inline it under cabinet between output chamber and nozzle. LNT also shipped it immediately. Would recommend both product and company highly. Best price too!

On January 19, 2010:
i have a 75 gallon tank that had a couple of large Cichlids. over the years , these fish had probably broke 3 glass in the tank heaters. my fish ended up dying , so i started over from scratch in baby cichlids (Oscars and Jack Dempsey). when searching for a new heater i came across this Hydor ETH heater. I was a little worried about using this heater , but it sounded like a great idea. well it worked out great with my eheim ecco 2235 filter . had to get line reducers , but was easy to set up and has been keeping my temp. a steady 77.7-78.5 degrees. wish I would have got this heater a long time ago. now I just hope it lasts as I have only had it for a month. Pet Mountain was the cheapest and had fast delivery. I couldn't be happier with this heater. Leroy

On January 12, 2010:
Awesome price for a 300W inline heater. Best deal I could find and great product!

On January 4, 2010:
This is an awesome heater. No more room taken up in the tank. No more burns on fish. I will never go back to a in tank heater again.

On October 27, 2009:
Awesome heater. Temperature does not vary at all and I keep the tank in the basement where the temperatures get into the 60s.

On December 4, 2007:
Great heater! Works very well and nice not having it in the tank!

On April 20, 2007:
These heaters are the greatest thing since sliced bread.Clearly the most efficient and accurate heater ever made.I just bought a 300w for my heavily planted 50 breeder to replace a stealth 200w which I thought were the best and safest until now.Temp. only varies .3 Degrees from day(lights on) to night(lights off).Its also a snap to install it takes about 5 min.

On February 16, 2007:
No more eye sore inside the tank and keeps a constant temp throughout the tank.

On January 25, 2007:
Perfect for larger aquariums, dependable and easy to use