How methane becomes fish food

Instead of counting sheep.. in winnie the pooh style – kept awake wondering what the equivalent of fish breathing and burping is – and finally gave up and got up and looked for explanation online and found this – it seems fish benefit from methane released by bacteria in lakes and the sea although not completly sure how the processs works.

POM and DOM are not fish versions of Ant and Dec but particulate and dissolved organic matter (please see link)