Comments: Good heater for the price.....

Comments: I am using my heater in my saltwater mixing tank. Out of box the temp gauge was right on what i set it to 78.I bought the 400 watt heater was a overkill for mixing tank but plan on using it for backup heater for 80 gallon tank if needed. Very happy with this heater and price would buy again!

Comments: This is a pretty good heater. Bought it for its size and it's perfect in my nano cube!

Comments: If you want to have a Friday night fish fry at your house with your fish, use these heaters. After about six months they won't shut off. Result- cooked fish!!

Comments: Hydor makes good products, but these heaters are terrible. I have a pile of them I need to send back to hydor because they either won't turn on or won't turn off after about 6 months of use.

Comments: I had the 400W version of this heater and when I went down stairs tonight I was shocked when I touched the sump. I found out that this heater had split open and was spewing electricty into the tank. The heater is less then 6 months old and its already died. I have had to Jager heaters for 6 years w/o issue. The only reason I didn't get another one of them when I bought this one is b/c I needed a bigger heater for a new tank. Worked good at first but like I said didn't last long at all.

Comments: Our house gets very cold at times and this heater does a great job in my 3 gallon tank. It fits well and doesn't take up much room. It is making it possible for me to maintain a healthy and happy freshwater tank. Couldn't recommend it more!

Comments: been using one for several years now - no problems. It's a pretty tough little heater - great for 10 gallons. It holds the tank around 80F when it's around 65F in the house.

Comments: Bought 2 of these to heat my 75 gal. saltwater tank. They has been a pain right from the start,hard to adjust,turned all the way down and they still raise the temp to 80 degree. Good thing I had a chiller or I`m sure my tank would be wrecked. Took a bit to figure why my chiller kept on coming on, this was why!!

Comments: I bought the 300 Watt unit as it fits my requirements... Its 15 inches long! I have to be creative with placement as its too long to tuck in my sump, my original idea. But it does have a very accurate dial setting. So I think its a decent unit.
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<br />Maybe you might buy two 150 watt units that are shorter to be able ti hide them out of sight.

Comments: the Hydor THEO heater performs marvelously. it keeps my 100gal tank at a solid 80 degrees and my 25 gal sump is in the garage, where the temp dips to low 40's. its also shatterproof, so i dont have to wait for it to cool before i take it out.

Comments: I was very happy with this heater for the fact that the features are true. First its durability, as i had dropped it twice on the floor right out of the box(I'm a butter finger). Not to mention that it IS accurate Within -/+1 degree. I definitely recommend this heater.

Comments: I don't care if you have a heater made by space aliens a million years ahead of us....use a temperature controller with your heaters, no matter what type of heater you employ!

Comments: Very nice heater. I've been using this brand for awhile and it works very well. I really like how durable it is. Very good quality. Temperature is accurate.

Comments: I bought the 50 watt Theo for my 6 gallon freshwater tank. I had to turn the dial down to 71 degrees to get it to shut off after it heated my water to 79 degrees. It's been running for 3 days with the dial at 71 and the water maintaining a temp of 78 to 78.5 degrees. However after reading all the reviews about the the heater sticking on and frying their tanks I will be replacing this one for safety.

Comments: Don't waste your money on this piece of junk. It is totally inaccurate (on the order of about 10 degrees fahrenheit) as several unsatisfied customers have noted here. Hydor should be ashamed of themselves for selling second rate products which have surely destroyed many an aquarium.

Comments: Ordered the D&D Salt Mix kit that included Refractometer and 200W Theo Heater 6.6kilos of D&D salt and Coral Vue digital thermometer.... The 200w heater was off by more then 3 degrees when using the Coral Vue digitial Thermometer and then using my personal digital high end wireless temperature thermometer; and the Theo heater did not shut off. I called them because the Refractometer was giving me false readings when calibrated with lab tested .35 ppm solution, so I told them about the heater too. They replaced it with the same device that, again did not shut off and was off at every point on the adjustment knob except at the 79 degree mark which sometime went to 80 before shutting off. I own a Theo 400 watt heater that hasn't given me any trouble, but the 200w batch must be off. I've read other reviews that mirror these sediments, but wrote them off, a bit, because I did not need the heater anyway, I just bought the kit for the salt and Refractometer. Little did I know that item was going to give me trouble too. I can't say enough good things about this store, as their customer service is superior in the trades, but some of the shipping methods and products have given me trouble over the years. You can buy from them with confidence that if there is a problem, they'll take care of you, but you may have to do some legwork. I think, for the most part, reviewers are accurate in their comments and I would stay away from this heater unless you're mixing salts, and don't care about the accuracy of the device. This has been my honest experience.

Comments: My Theo heater was purchased to heat my 100 gallon container of newly made up saltwater.Thankfully, I didn't put it in any of my tanks, because with the thermostat set on 79, it heated my water to 92.9 degrees. It was NOT stuck on. At that temperature, reducing the thermostat one click turns the heater off... verifiable thanks to the lighted "on" indicator. When I removed the heater, the temp dropped to between 76-77 degrees with the pump running. I would steer clear of this heater unless you want to risk nuking your tank.

Comments: I have three different models of hydor theos, unfortunately! One is in my 30 gallon, one in my five gallon, and a 400 watt in my 110 gallon (All are saltwater tanks). To say that the temp. gauge is inaccurate is a understatement. I have had my 400 watt heater set at 72 degrees and the tank temp is actually just over 81 degress and it is still turning on! This is verified by an electronic therm., 2 floating glass therm., and a "slightly" inaccurate LCD stick-on therm. All heaters in all tanks are not even close to accurate according to the temp gauges. I had to take the first 400 watt I got back to the store b/c when it was turned way down on the dial, it still was heating the tank to 86 degrees! Love your fish and corals and get something more reliable please for your own sanity peace of mind. I have been through four different Hydor Theo heaters in three different models, they just are not accurate or safe for your animals! They look nice but what does that matter when your animals are dead?

Comments: Seems to keep the temperature up. It's temperature indicator isn't accurate when compared to the tanks temperature.

Comments: First one I bought did not work. Hydor's response was that my thermometer was bad and not the heater. Second one worked for a little over a month and then I woke up this morning to find it went on last night and never shut off tank temp is 88 degrees farenheit. Heater was set for 79 and never shut off.

Comments: I needed a compact heater for use in a crowded chamber three of my biocube. This heater is perfect. Very easy to use and sturdy.

Comments: I bought two of the 400 watt versions, received and installed them exactly one week ago, and one of them exploded while I was at work and flipped the breaker. We'll see what choosing this product costs me in coral in the next few days...

Comments: I use two of these in my 54 gallon tank. They work great especially for the limited space I have to put them.

Comments: I bought a Jager heater for my 12g Nano Cube because the brand seemed to get a lot of praise. However, it was not fully submersible which was a huge inconvenience...the power cord was a pain! And the temperature seemed to constantly bounce (+/-) 2 degrees! I bought the Hydor Theo 50-Watt and it's really SPECTACULAR! When I opened the box I was surprised by how small it was...and so far I've had it for a few days and the temperature only fluctuates at most about (+/-) .2 degrees! I'm also able to fully submerse it horizontally so it's more hidden from view. I highly recommend it.

Comments: It is the little heater that could. I have a small 5 compartment Betta tank (Aprox 4 Gal.) and it does its job fine. I only gave it 4 stars because the temperature scale is not very accurate, specially at 80+ temperatures. However, once set, it holds a very steady temperature. I recommendo users to guage temperature settings with an external thermometer to establish the right temperature.

Comments: Having this one heater replaces 2 other 300 watt heater and keeps the water just as warm

Comments: I received the Hydor Theo 50 watt heater and it has worked wonderfully in my 17.5 Gallon Nano tank. The material and craftsmanship is absolutely top notch. This is the total throw it in, set the temp and forget about it heater.

Comments: My tank is currently 77.7 degrees according to my two internal thermometers - one in sump and one in overflow. I have verified this with a thermipen, my most accurate and an $80 temp reader. After realizing that my pair of Hydors were overheating my (thankfully) new and just curing tank to 83 degrees when set to 78, I set both of them to 74. One of them is on right now! You can't maintain 74 degrees by adding heat to 77.7 degree water! I read somewhere that these were good heaters - not true from my experience. Maybe I got 2 duds, but these are terribly innacurate.

Comments: I've had about eight of these heaters ranging from the 50 watt to the 300 watt. Last night, the second of these shattered and broke in my reef tank at 1AM. Two others I use in my RO/DI water tanks have managed to weld their thermostats in the on position, heating the water well past the 90's. That's 50% failure so far. Do yourself a favor and pass these up. I'll be buying titanium heaters for use with a controller from now on.

Comments: Worked very well, just as advertised.
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