Hi,
Mosses are generally defined as terrestrial plants although some are said to be aquatic. For those growing in aquatic conditions, they are not really true aquatic in nature because at times they do expose to air during dry season. No mosses are growing in ocean or in lakes, ponds, etc. Most of the aquatic mosses are found in streams or sometimes fens where they are immersed most of the time. However, I have found my friends who grow a few mosses in aquaria with air pumps and under a good light condition. I asked them how long the mosses have been in water and they said a couple of years had past. So, I guess it is possible to grow mosses in an aquarium, but I doubt they can survive for an extensive time, to say five or ten years. Anyway, it all depends on the condition of an aquarium.
It is hard to identify the moss you showed to me. It looks like a Plagiomnium species. For the name Plagiomnium trichomanes, it has been synonymized with P. acutum. So, its distribution is much wider now than it was previously reported from China and Japan as P. trichomanes.
Hope this is of some help to your inquiry.
