no worries, we learn from experience, my first mount didn't go very well for me either and if i am not mistaken, i change it additional two times before i am happy with it.
i use thread the one for sewing, so far i found it to be the easiest to work with, and black color with good camouflage (as in pic 2 on the upper right) and less problem with algae and the area where the string crosses the roots, just line with a string of sphagnum moss over it while tying.
just enough pressure and not too hard or u will damage the root.
i tried with other things like nylons fishing string, meat string and braided fishing line (best of all three but most expensive
)