ISTA I-H616 500W Inline External Heater

Great heater. I was a little apprehensive to use it since I had not known this brand and the few reviews about boiling a tank but those were simply user error. This 500w heater keeps my 55 gallon tank within 1 degree and draws exactly 500w when running and only a few watts while monitoring. As a warning to any new aquarium keeper ALWAYS USE A DEDICATED HEATER CONTROLLER ALONG WITH ANY HEATER! If you cook your fish due to a failed heater, it is your fault for not adding a redundancy shut down option. I suggest the inkbird thermostat heater control for around $35.00. great price for peice of mind.

I was happy with this external aquarium heater. It kept the temperature fairly stable in my 125 gallon tank. Yesterday I realized the tank was cold and the heater temp display said HI. So, I shut it off and put in a couple of immersion heaters temporarily. Today, I was hoping that a good cleaning would solve the issue, but it didn't. So I decided to open it. As you can see from the pictures, some water went inside, the insulation around the heating element didn't work well when wet. You can see the burnt/melted plastic parts and corroded power connection. The reason it failed was one of the temp sensors is open circuit. This is meant to work right outside the tank, attached to a water hose. It's natural that there will be water outside the housing, but that water is supposed to stay outside. All they had to do was to make the case water-tight either by using an o-ring around the case opening, or seal the case shut completely. One can get an electric shock with a product like that. They saved a dollar at best, and the product is dangerous because of it. Unless you plan on using it in a dry environment (ha ha) think twice before you buy.

I bought the 500w heater for my 90 gallon planted tank. So far it works perfectly controlling the temperature, even during a bout of Ich when I had to increase the temperature to 31 degrees Celsius (87.8 Fahrenheit) to kill the parasite in my tank (Ich must have come in on some plant material as I haven't added fish in months). Many complaints about hoses not fitting, but I used the 16/22mm hose as stated in the product description (by Eheim) and it fit perfectly. Warm the hose in some hot water to make it more workable over the fitting. The supplied hose clamping nuts can be removed if you use a different size hose, just add hose clamps. Would be nice if this product had a decimal accuracy, now it's just even degrees Celsius which gives a 1.8 degree Fahrenheit jump for every degree Celsius. If you are trying to keep a specific Fahrenheit temperature, you won't be able to do so without a decimal accuracy on the temperature setting. I printed a small conversion chart on a label maker for common temperatures. Unit does make an audible click when it turns on. Not an issue for me, but might be for some. Unit will fluctuate one degree until it turns on. My tank temperature still remains stable, but it's a 90 gallon tank. Smaller tanks may fluctuate. Unit will remember the set temperature in the event the power gets shut off. Also very easy to set and adjust the temperature. Digital display is nice. I only gave a four star review as I'm unsure of product reliability or longevity.

Was running a huge marineland submersed heater and my tank would dip a few degrees at night (when house furnace was turned DOWN), bought this so the temp would hold rock steady day and night and so i could have less equipment inside the tank. Easy install, I did use stainless worm-drive style hose clamps and threw the supplied plastic nut things away - heated my pump hose in hot water and slid it over the nipple and secured with clamp, easy. Set this to 25 Celsius and my water temp holds exactly 77.2 F day and night with never a dip or spike... SUPER pleased!

I did research before I selected this. I read all the reviews and was hoping to receive a flawless product as some people claim faulty ones. I did read the tube size issues and the clamp issues that people reported, so I prepared myself. I have a Marineland C series canister filter wich come with very thick tubing. The picture of this in line heater showed two sizes for tube connections so I figured one would work. As others have suggested, I purchased a clamp kit with it. I measuerd all my tubing out and connected them with ease and clamped them as shown in my photo. After getting everything ready I nervously got the filter pump started crossing my fingers for no leaks...SUCCESS! Now for the heater itself...I set it to 25 degreess Celsius to give my tropical tank a nice 77 degree Fahrenheit living environment. I also have a floating thermomiter and a digital thermometer that I put in to make sure it is still accurate. I watched my tubing connectiones carefully for about 30 minutes and then every hour for the rest of my day, each time looking at the temp and comparing. I was very surprised to see that the in tank floating thermometer and new heather were EXACTLY the same, 77 degrees. My digital only went to a 76.3 and 77.4...not once dropping or raising a full degree all day! I also read that some had water flow issues, but my water flows through this with the same pressure (eyeballing not by technical measurement) very good water current in my 40 gallon tank. I will give an update after long term use or if an issue arises. One year update: Never had a single issue with this running 24/7 (minus water changes) recommended to everyone.

Bought the 500 watt version. Compression nuts worked great on my Fluval G6 tubing. Installed it in the evening, everything looked like it was heating towards 78 degrees. In the morning there was moisture under the LCD readout. The button scrolled through static readouts, but they didn't seem to have anything to do with what is mentioned in the manual. The current temp always showed 38 and the target temp was always C. The led that showed that the element was heating was constantly on. The true water temp at this time was 74 degrees, near my room temperature. I have tried power cycling several times over a few days. Same result. At this point, I am not comfortable plugging it in. I have not tried the other in line brand to be able to compare.

I bought a 150w a few months back and its been working GREAT!!! i just bought the 500w for a different tank and the input/output are completely different than the one i bought previously, i planned on using hose clamps regardless but the main thing i am having an issue with is I bought the 16/22 mm and it looks like they now have both sizes on the ports to fit either size hose , so my main concern is now i am hooking up to a bigger size hose and the water will be coming out of a reduced size outlet, the 150w doest seem to slow any of my flow down and has the same inlet/outlet as pictured on the item to fit to size hose ordered, but my main concern is that with the tiny hole on top an bottom , it will slow down the flow of the bigger filter..... so really whats the point of buying a bigger heater if it fits a smaller hose, needless to say that 150w and the 500w are identical in size , will update once installed but for now, i can say i am a little skeptical.

Was great right up to the point I couldn't return and then just stopped working.