On May 3, 2012:
Works great. #1 in my books

On March 26, 2012:
Failed within the first year, which was very disappointing. At least the return & replacement process was relatively painless, less the return freight incurred.

On March 8, 2012:
I bought this 400 watt heater last year. It lasted 1 winter and it did not turn on again. To make matters worse the light stayed on so I thought the unit was working. Needless to say I lost a lot of fish and I have to shop for another heater. I will not buy a Marineland heater again and I would not recommend this heater to anyone. One star is a gift.

On January 29, 2012:
I had to replace all my heaters because I used all stealth heaters & they had a recall on them. I had over 30+heaters & had to ship 10 or so at time as I couldn't afford to buy 30+ heaters at one time. It took nearly one year to replace them all. I had know problem receiving the cash for the recalled heaters other than the time it took them to send it (a LONG time !!!) I replaced them all with Visi-Therm Deluxe Submersible's. So far all I do is send back NEW Visi-Therm that have failed 2-3 at a time several time's & they're very SLOW about it !!! I've noticed by reading the other review's that before 2011 most review's were ( GREAT PRODUCT !) & From 2011 to the present time all the review's are (NOT SO GOOD or BAD PRODUCT!!) Custumers & distributors need to bring call Marineland & make a complaint!!!!!! I have!! Contact-United Pet Group at (1-800-338-4896) & COMPLAIN !!!!!!!

On January 13, 2012:
Bought and installed unit last week in August of 011. Now it's mid January of 012 and I'd noticed that my fish were not eating and hiding a lot. After the second day I had the water tested and the water came back good I also noticed that the water felt colder to the touch. Looked at the gauge on the heater and it was reading 82F.Went and installed a digital unit in aquarium and the water was 64 DEGREES! I then ran out to pick up another heater rushed home installed. During the course of solving this problem I lost all my Cichlids with in hours apart  trying to get water temp. stable. When I removed the bad Marineland heater I noticed that when you jiggled it around it was broken internally. Even though it appeared to show signs of operation example: light on gauge reading set temp. correct it was not working period so, buyer beware. Yes they are priced cheap because they are cheap. Remember you get what you pay for. It's not worth loosing your fish such as I have and now need to replace.

On December 10, 2011:
I bought a 300w and was using it in my 65g salt tank in my basement. I noticed that my anemones were very small and my corals did not look very nice. When I checked the temp I was at 71 degrees and that was after my MH's had been on for 6hours, so at night I was getting in to the 60's. Checked the light on heater and it was green, so I cranked the heater all the way up. The thing is still green.... It lasted about 9 months... Do not buy unless you are using a temp alarm!!

On November 12, 2011:
I bought two 150 watt. Both come on way after they are supposed to be off! Seem to of by at least 5 degrees! I am very disappointed!

On November 12, 2011:
I bought two 150watt heaters for a new reef tank I just started up. They are light weight that is why I bought them as compared to Eheim- Jager. So far they are very poorly regulated. I have them turned down to 75 degrees and they keep the tank above 81 degrees. Both of them come on way after they are above the set temp. I should have gone with Ehiem-Jager.

On October 18, 2011:
This was my first heater purchase, and I was impressed with how easy it was to set up. The suction cups hold well without the need to press too hard against the glass when attaching them, and the paper inside the box tells you how to order more if you should ever need them. The dial is easy to turn and easy to read, the light comes on to let you know when its heating, and my tank has held a steady temp since I started using this. Before I had the heater my tank was registering anywhere between 70 & 76 depending on the room temperature, and now it holds at a steady 80 degrees. :)

On March 15, 2011:
The heater worked fine for a few months. Then, this heater never seemed to work that great in terms of maintaining a stable temperature. Now it's completely failed. The light is on but it's not warming the water at all. Temp dropped to 77 degrees. Very disappointed. (I have/had the 400 watt model in a 100g tank)

On February 27, 2011:
Works well, it keeps temp warm at desired position I would recommend it

On January 25, 2011:
Received product for set-up of a new tank. Very easy to use and place in tank. Double suction cup holder keeps appliance in place securely-I have some monster-sized fish that actually broke the other heater. Worked quickly and shortly after set up the water was ready for the fish.

On January 25, 2011:
This heater worked for a day. I have it cranked all the way to the lowest setting and it still turns on to heat. Woke up in the middle of the night and temp was at 81 degrees! Not a great heater!

On December 26, 2010:
I bought this heater because my old house has drafts and I was having a tough time regulating the temp in the water for my tank. I put this heater near the filter intake so the warm water would be sucked up and dispersed evenly, and so far I have had no issues in maintaining a steady 80 degrees. This heater works perfectly in my 70 gallon tank.

On December 14, 2010:
I had purchased the best heater Walmart offered, but it only lasted 8 months so I decided to upgrade to this heater and see what happens. This is a new purchase so long term durability is not known. What is known is that it seems to be built better. It also has a temperature control knob on top with temp markings, and when I set it for 80 degrees it actually heated the water to 80 degrees. The only minor problem was that the bottom of the heat tube contacted the side of the tank when the suction cup bracket was at the top per it's instructions; so I took the old suction cup bracket off the old Walmart heater and stuck in on the bottom to hold the tube away from the tank. The star rating for this unit is premature due to no long term usage, but for now I gave it 5 stars to be reviewed a year from now see if there was any problems.

On September 26, 2010:
you have the best selection and prices

On September 25, 2010:
Simple, durable. I have had one of these for over a year and it has been reliable so far. I like the indicator light to let me know that it is working. Best thing to do is to keep a well fitted lid on your tank to help retain the heat. This also helps to lower your electric bill.

On April 28, 2010:
I researched for the best aquarium heater for my 100 gallon tank. I decided on the 400 watt Visi-Therm because of its solid reputation and power output. I was worried it couldn't handle my volume, but now I think this heater's capability is underrated. It raised my 100 gallon tank's temp from 65* to 78* within 18 hrs. and holds it within .5* steady. I located it in the back corner, next to my filter intake so that the water will be heated as it suctions and then discharged to the opposite end of the tank. My entire aquarium temp is even with no hot/cold spots. I highly recommend this heater.

On February 2, 2010:
Heater works well and is easy to adjust. Temperature level is nice and easy to see. No complaints.

On December 1, 2009:
Keeps the tank within 1 degree throughout. This may change in your tank depending on water flow. I also noticed a drop in power use. I have a Kill-A-Watt meter on my whole tank setup, when its on it uses the same amount as my last two heaters I used to do the same job as this one. It looks pretty neat too.

On October 18, 2009:
I bought the 25W version and it worked great for like 3-4 days, but then started not shutting off when it was supposed to. It got so bad that I had it set to 76F and it was 85F in my tank. My poor betta, I'm glad he didn't get cooked in there. I thought it was my thermometer at first, but that wasn't the case...bad heater. I'm sending mine back for a replacement in the hopes that I just got a bad one.

On February 29, 2008:
Best heater for the $$.. Have had excellent luck with it.. It stays on the glass and seems to keep very consistent temp.. Highly recommended..!!!

On January 8, 2008:
I've used at least 5 different heaters to heat up my 120g aquarium. I've had the titanium ones almost nuke my whole tank when it hit 110 degrees, my Ebo heater that was supposed to be superior doesn't even come on, the low end brands break, but this Visi-therm is the best! I put this heater in my sump and the temp does not budge when I set it! I am amazed! It is reliable and if it holds up for a year, I'll get another one for my water change tank. Very easy!

On December 13, 2007:
I found it to be a bit off on the temp, but consistant. That made it easy to make adjustments...

On August 9, 2007:
My Visi-Therm Heater provides such a stable temp for my marine aquarium. It is a great addition for my aquarium since it keeps the temp at the exact degree that I want it, and it keeps it at that degree. This heater has provided me a great deal of relief because I know my aquarium is at the perfect Temperature

On May 28, 2007:
I stupidly went cheap on my last heater. I have always had the Visi-Therms and Ebo Jaggers. I was in a rush because I was having aggression issues and had to get another tank running, so I ran to Walmart and bought a submersible Whisper heater.

It was total junk. It kept over and underheating. Luckily it was a tank with tough fish and I didn't have any losses.

For the same price, I could have ordered a visi-therm delux from Petmountain. These are great and totally reliable.

As for sizing, I recommend more wattage than Pet Mountain per gallon. Marineland has the following suggestions. Since I am up here in Maine, I stick to the higher sids of wattage to deal with the cold temps (especially the summer nights).

Visi-Therm Deluxe 25 25 watt for 5 gallon
Visi-Therm Deluxe 50 50 watt for 10-20 gallon
Visi-Therm Deluxe 75 75 watt for 5-25 gallon
Visi-Therm Deluxe 100 100 watt for 10-40 gallon
Visi-Therm Deluxe 150 150 watt for 20-50 gallon
Visi-Therm Deluxe 200 200 watt for 25-65 gallon
Visi-Therm Deluxe 250 250 watt for 65 gallon
Visi-Therm Deluxe 300 300 watt for 75 gallon

On April 22, 2007:
The Visi-Therm Heater is a fantastic heater. It is so easy to use. I just set the heater to the desired temperature and it does the rest. If temperature adjustments are needed, it is as simple as a turn of the knob.

On January 25, 2007:
This heater is a great product. The deluxe version is so much nicer than the basic one. I'd recommend this to anything. Make sure you get enough watts for the tank though. In order to raise 5 gallons of water 15+ degrees and keep it level we have to use the 75w model.