Originally Posted by mjoy79
I agree with Jodah.
If you have betta(s) or other tropical fish, they thrive in temps in the 76-82 range. A preset heater will typically heat the tank a few degrees higher than the surrounding room temp. An adjustable heater will work a little better if your room temp is lower than 73+ (which it tends to be especially in winter)
This is one of the biggest misconceptions I see floated around here. A preset heater SHOULD heat the water to its preset temprature, it has no idea what the outside temprature is, only what it's thermostat tells it to shut off at. An inadequate heater will only heat the water to a few degrees above the surrounding temp because its internal thermostat never makes it to the temp required to shut off.
That being said, your betta should have a heater, but he will certainly won't die without one. Also don't skimp here, you can tell your parents there is a nice Fluval 200 watt on Amazon for 18 bucks, and if they spend 25 it's eligible for free shipping. It's a very nice high quality heater, is adjustable, and will work awesome in a 10 gallon even if it's open top.
The Phillipines you say!? That changes things. I really don't now what you have available there. Are your outlets 220v?