Originally Posted by tngirl92
A 25W will probably boil him alive in a tank that small. You need a 10 watt or smaller. I have a 2.5 gallon tank and I use a 7.5W heater. I recommend either of these:
I use the first one and even though it's not adjustable, it never has raised my tank above 82 degrees in the three months I've had it. It does great! In your smaller tank, you would want to buy a glass thermometer from the pet store to hang on the side and monitor it closely. If you notice the water getting too hot, unplug the heater. It's that simple!
This is not true. It will take some playing around, but if you test the heater in a bucket first and monitor the temperature, you will find out where to set it to keep the temperature constant. I have 25 watt heaters in both my 2.5 and 3 gallon tanks, and a 50 watt in my 5.5 gallon tank. I had to mess with the setting to get them perfect, but my tanks never get above 80 degrees unless I intentionally set the heaters higher.
You definitely do need a thermometer! And a glass one is the way to go, the strip thermometers are notoriously inaccurate. I have one on the side of my 2.5 gallon (leftover from over a year ago) and it frequently gives me inaccurate readings of 75 degrees when the temp is 80!
I would definitely recommend an adjustable heater. I used to have a TopFin 7.5 watt heater and it was horrible. I had to monitor the fish constantly and I worried the temperature would shoot up, so I was forever running in to check on my fish, waking up anxiously in the middle of the night, etc. I never saw it go above 84, but that was because I would always unplug the heater and let the tank cool down, but that's not good for a betta. Constant temperatures are where they thrive. :)
best of luck to you!