Here is a review left by a customer on a product. Would you say he was satisfied or dissatisfied?
Title: Doesn't warm water
Review: This heater was not sufficient to warm 20 gallons of water in my turtle tank. I would often check the water and it would be cold to the touch. Also, you aren't able to adjust the temperature which is not ideal when you are nursing a sick turtle and need the water to be around 82 degrees versus 78 degress. I would recommend the Aqueon 06107 Pro Heaters Submersible Aquarium Heater, Various wattage. These heaters are protected so your turtle can't break them. They are nearly indestructible. I bought this at a local pet shop after the tetra heater didn't work and it works great!!! Don't but this!
