Well, upon further investigation, it appears that my sump isn't deep/wide enough to fully submerge the heater. How much of the heater must be in the water? I don't have anything in the tank now, so I suppose I could just play with it to find out if it will heat properly or not. Just wondering if yours goes all the way in...
Wow, so many "that's what she said" lines in that paragraph.
Most heaters are designed to be fully submerged. Evaporation is going to cause the water level to get lower and lower and if you start out with some of it exposed, chances are one of these days you might find an overly-exposed heater that's fried or cracked.
Ahh, so physical damage to the heater is a worry. Then I'll just leave it in the tank. It's a definitely meant to be fully submerged, because it is now, but I'm not sure what brand/model at the moment.
Eh, well I live in Florida. I'm not too concerned with it getting too cold. I have the heater all the way down... it's December... and the water is 79 degrees. Guess I'll be looking at a Carribbean species :)
I would suggest leaving the heater out of the tank altogether if you are in FL and don't keep the AC on high. They are really not the best thing to come in contact with for curious critters of any kind. I am in the N. GA mountains and have only recently decided I needed a heater in ONE of my tanks because the sump is in front of a window. If you can pickup one of the inexpensive Coralife thermometers (nice little digital for tanks) they are easy to read but a stick on works too. Monitor your tank at different times during the day and see how much it changes (early AM will likely be your coldest but monitor for your hottest too to check your daily fluxuation). What you WILL likely need is a PLASTIC clip on fan over the sump to keep it cool during most of the year. The fans can be found anywhere from a couple of dollars to around $35 for a double fan built for an aquarium (I use several different kinds).
I have tried several and found that the most recommended has been the best, a THIN layer (1"-1.5") of argonite sand. It is the easiest to clean and my nitrates have been much easier to keep under control since I switched.