Methanogens Living at the bottom of the pond, furthest away from oxygen are the methane producers. These microbes also live in murky swamps, where they produce swamp gas, also known as methane. When there is no oxygen nor other electron acceptor, organisms called methanogens proliferate. Usually, the bottom of a still pond has no oxygen and is home to methanogens. For more information on methane producers visit the Cow Rumen .
Ponds are a fantastic source of microbes which are easy to see with the proper magnification.
Compare the types of microbes you find at the top of the pond with those you find near the bottom of the pond.