I bought one of the 75w Cobalt neo therms to go into a 20L because it was one of the shortest heaters I could find. I have not set it up yet but is supposed to be super easy to set. They did have some issues with a batch of 200 watt neo therms a while back and there were quite a few that had them melt and leave a horrible burning smell. No recall ever issued but it sounded as if Cobalt took care of the issues and they have since changed that heater a bit. As to the regular glass types I have not used it or heard good or bad about them.