I got the visi-therm stealth 100 watt heater for my 20 gallon tank today. I have noticed the difference immediatly, with the all-glass heater i used to have the temp would go up and down 1-2 degrees all the time, it would either be like 83 degrees in the morning, and 80 degrees at night, never stable. But with the stealth, it is at a constant 81 all day. Thanks everyone for the suggestion, im sure me and my fish will like it a lot. Now i dont need to worry about a heater over-heating and cooking my fish 