This is the first winter for our pond. It about 20 feet long, 8 feet wide and 3 1/2 feet deep. It has a bog that is about 40% of the ponds surface area. The bog is fed by two pumps, one to a waterfall and one to the plumbing under an eighteen inch deep bed of river pebbles/gravel. I am in zone 6, St. Louis, MO. The pond is stocked with young koi and goldfish. I need to buy a deicer, but I can’t figure out what to buy. There are way too many choices. I am riddled with indecision! Please save me from my paralyzing indecision.