I researched just about all de-icers before buying one.I've read that floating de-icers are best because they will just about guarantee that a portion of surface area won't freeze.During extreme temps it is recommended you shield it from strong winds.Sinking de-icers may not,depending on the depth,give that kind of assurance.The one I purchased is backed by a 3 year guarantee.It doesn't need a seperate device to protect it from contacting and burning the liner.It is safe against any type of liner. It's called Farm Innovators Ice Chaser. I paid $33.00 at yourpondstore.com.It's rated at 1250 watts.Purchase the TC-3 thermocube($12.50) with it-a must.It will cycle the unit on at 35 deg and off at 45 deg.and cut the energy usage.There is a de-icer that uses 150 watts called Thermopond and claims it works but I've read their have been many problems with them.