Hello and welcome to FishForum. Yes, I have my males in 1.5 and 2.5 gallon critter keepers. I have a Marineland stealth visitherm 25 watt heater in one and a Tetra whisper 50 watt in another one. It doesn't work as well as the Visitherm. Your fish will be more active in warm water.I plan on ordering another Visitherm soon for another one of my males. My females are in gallon containers with no heater but my room stays pretty warm all winter. The Visitherms are adjustable but the Tetra whispers are not. I hope this helps.
Saw your bettas are in 1 or 2.5 gallon tanks. I thought you might be the best one to ask.
Does a male need more than one gallon.... I notice you have yours in 2.5.
I'm having trouble keeping the water temp regulated in this little tank. I'd like to keep it constant, but it gets either to hot or too cold. If I let it set with the heater on, it goes to about 86... that's too high isn't it? But, without it and with just a 7 watt bulb, the water only stays about 76 and he doesn't swim around much at all. When he does and it's cold like that.,.. he swims kinda spastic like. He just darts. Like electric shocks. That is.. when he's not just sitting at the top of the plant closest to the light. He's also hard to rouse for breakfast. I usually keep him moving frequently during the day. That's what made me think it was the temp and not some illness. I'm sure there are heaters with regulators, but they are for 15 gallon and above... Any suggestions? Thank you in advance for your help.