The 200W had an "exploding" issue several years back but that has been resolved, supposedly
I use 3 100W on my 53G, zero issues after one year, they've been great. They are not necessarily perfectly accurate, but once you figure out how much off they might be and accomodate for that, the temperature variability is very, very small. For Example, I have to set all three of mine at 80 degrees to maintain a 77-78 degree water temp but the temp does not vary from 77-78
These require more wattage per gallon than Eheims for example. Two 100W Eheims would have heated my 53G, but two Neotherm 100W was not quite enough for my tank and I had to add a third
