[VivianKJean]

yes, please answer ALL of the above questions.

Do you know anything about cycling your tank? Is your filter a bubbler or is it an actual filter (with a cartridge in it)? If it is an actual filter you need to educate yourself about the nitrogen cycle. below are some links.

http://www.bettafish.com/showthread.php?t=111960
http://www.bettafish.com/showthread.php?t=107771
http://www.bettafish.com/showthread.php?t=47838

Here are some videos on it was well
https://www.youtube.com/watch?v=bK_D_1CyUCs
https://www.youtube.com/watch?v=6W92KuT-T8A

 

[VivianKJean]

I would do the water bottle method over the lightbulb since the bottom would be warmer then the top.

Honestly, I would try to heat it with a DYI system UNLESS you have a thermometer because otherwise you will no have idea what the temperature of the tank is.