Originally Posted by xMandy
Mollies and guppies are both tropical fish and need warm water. At night your room temp most likely drops and it doesn't help that your water will already be cooler than the room temp. Maybe you could get a power strip? I'd read up more info than we could give you. Remember just like any animal you should know a lot and research before you get it.
I use to keep guppies and while it's just like keeping any other tropical fish.. You need to know common illnesses to look out for with them.
Agree 100%. And, it will probably take longer for you to ask for info on those fish and receive the advice than it would take for you to do a quick google search and find many different sites.
But, yes.... they both need heaters to maintain a stable temperature of about 74 to 80 for mollies, and I don't know about guppies, but would imagine they'd be similar. Your room temperature will always be several degrees warmer than your tank water temp, so a heater is important unless you live in a place that's always pretty warm.