Beware - I put one of those flat submersible heaters
in my betta's 2G tank under the gravel - and it's dangerous! It doesn't shut itself off but heats continuously, so on day 2 (day before yesterday) I found the temp to be 88 degrees :mad2: ! Luckily, the poor fish seems to have survived unscathed. Now I'm looking for a replacement heater and in the meantime I keep unplugging and re-plugging the aforementioned piece of junk to keep the temp somewhat stable around 78.