Posted a similar thread in the noob forum. Now that it has come to my attention that I do indeed need a heater, what kind? I have a Nano Cube 24DX. My temp has been hanging around 72f-76f. I looked for a Nano FAQ area but didn't see anything...
Lutra, You will definitely need a heater for any tropical reef setup. I use 2 50w units for my 20gal nano which I keep at 78. Having 2 heaters allows for one to fail and still leaves the other to heat the system until I can replace it. Also, if one sticks on, a lower wattage unit is less likely to get the system too hot. In my 20 years of tank-keeping I have had 4 heaters fail and 2 stick "on".