So, i have a 400w marineland heater. Bought it new back somewhere around March of 2010. Couldnt keep the temp stable in my 120, so I moved it to my 75. Temp will not go above 74. Turn it on as high as it goes and still stays at 74. I also have 2 Hydor 400w heaters, one is in my 150 and keeps the temp perfect. When I put the other in my 75, it seems no matter where I set the temp, it goes to 86! Anyone have any good suggestions for heaters? Or is there something I can do?