If you are located in warm, humid area, you can have your potted moss planter bottom part in water.
Please note: any indoor environment with air conditioning is considered dry.
The following is an orchid and moss planted in a natural lava rock planter.
Inside the planting hole, sphagna wraps the orchid roots and fill the planting hole. Then I place two piece of Hypnum plumaeforme moss under orchid roots.
The whole piece is placed in a deep tray. By this way, both the orchid and moss live well. The porous lava rock is moist which lead the moss spreading on it.
The follow photos show moss planted in a small lava with drilled holes.
Again sphagna is used to wrap moss roots and filled the hole. In a close container, this is moist enugh. Just spray water once or twice a week will be ok. A more lazy method is have some water in the bottle, water level below the middle of the rock.
This is how to store your moss, small bonsai indoor in a low maintenence way.
take out a fish tank, those high one will be better.
put a filter plate at bottom. I use small lava rocks instead.
put your bonsai, potted moss inside.
pour in some water, the water level should be a little higher than the filter plate or lava rocks.
if your plant likes dryer environment, place it in a higher position; if it likes humid environment, the place it lower, more close to the water.
Have them under a LED grow light so you can put the tank anywhere in your room.
I do not use any filtering system and the water is always clean because I use lava plnaters and sphagna at bottom of plantes and they are natural filters.
