Light? OMG now you're cuting a sensitive angle 🙂 this is growing under 3 ledstrips 7 watt 600 lumen each. I also dry started my tank for several weeks. The Fissidens came in last the same day as the fill up and that was i believe about 2 weeks before the first picture from above +/- few days. I don't realy know why this rocks like that, its my first Fissidens ever, so it might be the quality also helping a hand. I bought it from Aquamoos.de, i believe that's the growhouse from Flowgrow or Aquasabi dont realy recall that. But their quality plants are very nice and fresh. (Although the Marcandra Mini type 2 quality sucked, but that oe is new for them too) The only thing i did out of the ordenary is as i said in my first reply using root stimulator to spray all over the tank. And i cant help it all the moss and plants are rooting and booming fast and well. Except teh Pogostemon H. and the Utricularia graminifolia that last one is my own stupid mistake. The rest of the mosses like Santa Claus, Mini Pelia and Fissidens go like crazy. The christmass moss i already had to prune for more than 3/4 portion of what i initially did put in there it grows like weed and ruining my scape. I see in the stem plants that my light is at the low side, now i extended it with some more heavely ledstrips 2 x 12 wat extra, for a few days now do not know yet if it does anything better. Th emosses and bolbitis don't care they grow exeptionaly good. Im pruning on a daily basis.. Feel like Sir Prunalot..
I believe in that root stimulator because i have used it a lot on f.e. tomato seedlings and all other seedlings as well and on what i used it did always grow much faster and better than the ones without. So i thought cant be bad for swamp plants, also sprayed on the wood of course where the mosses are.
Soil is akadama if you like to now, so no firts in there in the beginning..