under perfect conditions and temps it can grow stupidly fast like double in a matter of months, i keep mine in a cold water FBN tank can its grown a bit but not huge amount
Old thread, but I just wanted to point out, temperature isn't the deciding factor for growth rates with Java moss, it actually does better at lower temps. lol
Lighting is a bigger factor, I find it grows fastest in tanks with a lot of light, better that than algae though...