yes, you do need some light, but since you didn't say what light you have or how long you leave them on, can't say if you need more.
use a toothbrush (new) and brush the coraline you have now, this will help it spread,
Also you had add
Kalkwasser Mix (as long as you're going to test)
Test your ca level.
read
this thread and search, this post is on the main page with yours, which may be why you didn't get any responses