Originally Posted by Sharrrky
Thanks for all the information. I have a new betta now its purple pink and blue like the sunset. I am looking for a heater for smaller tanks.
Marina makes a preset heater for smaller tanks. The 10w is the one you would want. However, adjustable heaters are better. Just remember that if you do a 100% water change, to acclimate him to the new water's temperature (as you discovered, very painful results), or if you do a 50% water change, then make sure your new water is fairly close to the tank's temperatures - slightly colder is better than warmer (for reasons you have already discovered), but not too much colder. My fish will tolerate room temperature water when I do a 50% water change, but she doesn't like water warmer than what she is used to.