Many types of land mosses grow underwater.
It is necessary to clean land moss from any and all dirt before submerging it underwater in your main aquariums. Moss does not have roots.
So, probably the cleanest samples grow on rocks and walls…
Two Ways to Grow Land Moss Underwater, by Michael Langerman
Can you put outdoor moss in your aquarium? : r/PlantedTank
Two Ways to Grow Land Moss Underwater, by Michael Langerman
Where to Collect Land Moss for Aquarium
Preparing Land Moss to Grow Underwater Update
Preparing Land Moss to Grow Underwater Update
Land Moss Sustainable Aquarium Garden, by Michael Langerman
Preparing Land Moss to Grow Underwater Update
Preparing Land Moss to Grow Underwater Update
Two Ways to Grow Land Moss Underwater, by Michael Langerman
Where to Collect Land Moss for Aquarium
Can you put outdoor moss in your aquarium? : r/PlantedTank
Two Ways to Grow Land Moss Underwater, by Michael Langerman