I have had this running on my 46 bow tang tank for just over 3 months now and couldnt be more pleased. Installation was rediculously easy. My temp is always constant and rarely fluctuates more that 1 degree.
My only peeve thus far...
The temp dial is off by 2 degrees, OR all of my thermometers (2 regular and 1 digital) are off. Probably not the latter.
As far as it breaking and boiling your fish, i have not seen this yet, however i will keep an eye out for it since i check my temp at least twice a day everyday. Will update this review if anything changes.
I would reccomend this to anyone who has external filtration, and $40+ (unless you catch it on sale like i did) to spend on a heater and doesnt want more junk in-tank.
Have a great day.

Easy to install, super reliable and accurate... I never notice it licking on and off...

I purchased one of these heaters because of the benefits that everyone wants from an in-line heater. I ordered it, and at the online retailer (and on other sites) it said it could be installed upright or flat. So I planned on installing it horizontally in my cabinet when it arrived. However, when it arrived, the box and the manual said that it must be installed vertically.
Well, since all those other sites said it was fine i went ahead and istalled it flat.. BIG MISTAKE!!
I almost killed the heater! It kept switching on/off in rapid successsion, like a car starting with almost dead battery.
So the companies italian-based website was no help, since the FAQ's were removed, and the site seemed half abandoned.
I spent over 2 hrs on the net researching the orientation issue, checking to see if that was the problem. Finally, i found a site with (old) forum postings that there were 2 batches of product boxes and manuals.

The first, had pictures depicting and manuals stating, that it would work in either horizontal or vertical position. However, sometime later (probably after reports of failures), a second box and manual were printed stating to install it only in the vertical position to avoid possible back-flow issues.

However, there are out there still some of the old boxes and thats why some online-stores and forums say it'll work in both posistions. I've installed it vertically now, and no super-clicking. Something buyers should keep in mind.

I am running an ETH 300 on both my 75G SA setup with an Eheim 2217, and my 125G tropheus setup with an Eheim 2260, and they do a great job on either tank!

never used external heater before. Works great and is hidden in the cabinet. I use 2 300watt for a 200gallon on 2 Eheim 2028 filters.

I like the look and temp controls are easily reached without getting wet.

Not sure I like the loud clicking sound but I guess I know it's working.

I hooked up a power meter to them to see if they were any less efficient. I had a 300 watt submersiable heater heat a 220G tank easily. The dual 300watt externals seem to be on more than the single submersiable heater.

I think they are less efficient and consume more electricty then a submersible heater since some heat is lost that never reaches the water which doesn't happen with a submersible heater.

I didn't compare two heaters but I would estimate they use 15% more electricity.

Overall the benefits out weigh the extra electricity.

I purchased this heater about a month ago for my 55 gallon, and was fairly skeptical. The C-360 I had bought came with a slightly larger hose than what fit on the heater, but I purchased some of smaller vinyl tube and some hose clamps and it fit snug. I set the heater at 78, turned on the filter and have not been dissapointed. I have two different thermometers at different ends of the aquarium both reading 78 constantly. I have never seen any flucuation at all. Aside from the installation, which was no big deal, I would say this is one of the greatest aquarium products ever made. A must for any enthusiast who does not like tampering with their heater to maintain the perfect temperature. I have kept my room very cold sometimes around 50 degrees with the windows open and never have I seen the temperature waver. Great product!!!!!

this heater is really set and forget. I hated having to see the crappy heaters inside the aquarium, this filter is the best. It does make a clicking noise when it turns on but I think it creates a piece of mind that It's working.

Accuracy is astonishing. One less piece of junk to see in the tank. Nice quality. If you have a canister this is the way to go!

I bought the 300 watt for my 65 gallon and will eventually move to a 125. I'm very impressed. Temp is rock steady, and I actually like hearing the little click indicating when it turns on and off. A bit costly, but highly recommended.

I have the 300W version on my 120 and it holds the temperature perfectly. It was easy to install and I love the fact that you don't see it in the tank. I have had no problems and would highly recommend this heater to anyone.

This heater is awesome. No matter what you set, you can bet your thermometer will read that temperature, provided you're using it in a suitable sized aquarium.

Can run dry in case you make a mistake. (I have)

Easy to setup, splice the tube, plug it in, and twist the sealing nuts and you're good to go.

As said, wont break a sweat no matter what temperature you set it to.

Only complaint is when it flips on/off it does make a slight audible click, but its not very noticeable unless you're really listening for it.

Just got another heater, the 300w one. Previously, my ebo jager couldn't manage more than 79.3 (was on all the time) due to the cooler house temps. Plugged in my 300w Hydor Eth, within 5min the temp was rock solid at 80.1 and the heater was actually off!

I have 2 of these for my 75 gallon mixed African tanks. I set them when I bought them 2 years ago and havent touched the since.

I periodically check the water temp and it stays wintin a degree of the setting.

They are little bit cumbersome when I do filter maintenance because the they get banged around when I take the canister filter tops off, but other than that they are perfect.

I have the ETH 201 200W version hooked up to the output hose of my Filstar xP1. This heater has proven itself to be reliable and keep the tank at a steady temperature. It is the perfect accessory to the canister filter since it doesn't take up any space inside the tank.

My large cichlids were breaking glass intank heaters left and right, I would find out by getting shocked. Saw this online, on sale, bought it and hard plumbed it between sump and a 150 gal tank. Had to buy hardware store hose clamps because of 1200gph magpump vibration. After 2 months bought another for my 100gal tank.Both tanks are in a basement that falls into the 50s in winter, no problem. Out of sight, no replacing because out of the way of cichlid attacks, for my money fefinetly a good deal.

i have the 300W running with my eheim cannister for my 75 gal tank. one of the best investments thus far. keeps the tank at 78 degrees without any noticable changes. it does cost more then an in-tank heater, but worth the extra bucks for the cleaner look.