Phal - gnats & medium question

[salvador1970]

Hi Everyone. I attached 2 pictures of my first Phal(the one that made my addicted!). Fortunately, it has started a spike, but I am worried that so many gnats are hovering in the bark medium. I do not want to re-pot it till it finishes blooming.
As you can see, it also has the bottom leaf yellowing, which normal I presume, and what you cannot see are two new roots growing.

Do you guys think I can add on top of the bark a layer of coconut mixture to cover the new roots? Will it help with the gnat problem? What solutions are there to get rid of these fungus gnats?


Thanks

Fadi