Riccia, christmas moss, java moss, or flame moss
I have a 10 gallon and dwarf sag in the back. I don't know what to fill the foreground with. I'm growing whatever on a slate and hopefully it will spread. I only have 2 pieces of riccia because some guy grabbed it by accident. I have a ton of java moss, but will it grow a good carpet, i never saw a good java moss carpet. I have a small amount of christmas moss and flame moss.