What the hell are Hydro sponges? We don't get many new ideas in Newfoundland and the products available are limited - hagen. Will a layer of peat soil below an 1.5 inches of sand turn the water tea colored. Is this setup good for growing plants. And Finally is two 30 in flores. tube enought to grow plat in a 36" by 16" by 20"Tall tank. Sorry about all the questions!