So I don't know if anybody out there has even heard of these critters, I certainly didn't until just the other day. Archaea were viewed as prokaryotic bacteria until recent rRNA sequencing has shown major differences between Archaea and Bacteria, and thus placed them in their own kingdom of life. They tend to be a lot smaller than bacteria and reproduce asexually. They used to be considered as extremophiles (only living in the harshest conditions: ocean floor vents, high Ph hot springs) but recently mesophilic Archaea have been discovered in places such as soil and fresh water. These guys are really interesting, but for the purpose of this post I have already provided more than enough background information. I encourage you to do some googling on the topic if you want to learn more. The point I am getting to is that there are Nitrifying Archaea, and they are more than likely working hard to continue the nitrogen cycle in your aquaponics system. The Nitrosomonas and Nitrospira bacteria are just pieces of the puzzle that is the organic chemistry of nitrification. Recent studies have found that in some cases Archaea outnumbered Bacteria in aquarium bio-filters (http://www.fishtanksandponds.co.uk/aquarium-science/nitrification-b...) . So come on, I know we will have to rewrite articles (maybe add a new section into the newest edition of Aquaponic Gardening, Sylvia) because of these little guys, but lets not be afraid of change!