I can tell you to stay away from Fluval E series heaters, oh they are good heaters, keeps good temp, has different light colors to alert to high, low, or correct temp range, BUT if you don't put them in the "perfect" water flow area of the tank they constantly flash LF (low flow) at you. I have a 220g in a 3 glass wall sunroom, so even with the room having it's own heating unit I need 3-300watt heaters. It was a royal pain in the backside to find a place of flow that all 3 heaters were happy with!!! Maybe in a smaller tank it would be such an issue but you have a 100g so I'd stay away from them (unless you really like a challange). I would have loved to go with an in-line heater, which supposedly gives you the most consistant water temp, but in order to get one with a large enough wattage for my size tank I'd have had to spend a bloody fortune. But I'd check into in-line heaters if I were you.