The weather's been cooler lately and I'm having trouble keeping the temps up in my 20-gallon long. I'm running a Cobra UTH mat on the warm side with a Herpstat thermostat and nothing on the cool side. The past couple days, it hasn't been able to get past 86 on the warm side, so I'm going to get an emitter. I'm wondering what wattage would be appropriate. I'm thinking either 60 or 100. I'd REALLY appreciate any advice.

While I'm at it, I'm going to get a ReptiTemp 500R thermostat to control the temperature on the cool side--I have a UTH for that end that I'm currently not using but figure will come into play as summer ends.