Submersible Aquarium Heater

Can you fix a heater tank? I have a few cheap glass heaters in my tanks for breeding, as http://s3.amazonaws.com/tc-photos/11442/product/giant/105453.jpg and are cracking on me when I never get them out of tanks (due to temperature difference). I wondered if it would be safe to use aquarium grade silicon to close the glass again. I […]