I need to purchase a heater for my already mixed RO water before putting it in my aquarium. I keep my system on a porch area and the water is much cooler than the aquarium water. I've used aquarium heaters but they haven't helped much. I would like something larger (fast) that I don't have to keep plugged in all the time (I mix my water in advance). I was thinking about searching camping equipment..... I have not been able to find this question using search so I'm guessing not a lot of people have this issue. I live near the Gulf Coast so the temp never gets really cold...... unless it's time to do a water change. If anyone knows of something that would work (not necessarily aquarium equipment) I'd appreciate the input.