Oh, I would definately do a greenwater approach, but not in advance of the clownfish larvae.
The objective is to keep the tank as bacteria free as possible for as long as possible.
Here is my thinking:
Start sterile, dechlorinate, add larvae. They will not eat in the dark, and they need their rest after busting out of the egg, so turn the lights off, and don't feed them until morning.
Feed them rinsed rotifers, but not the nasty water the rotifers have been growing in! Add live phyto to the tank , just enough to keep the rots nutritious, just a tint of green. (Don't add needless bacteria and poop. )
Hopefully, the rotifers will be eaten before they do a lot of pooping, and you can add some more rinsed live rots. If not, you need to siphon the poop off the floor and keep the tank tinted green with the phyto, so the remaining rots stay nutritious.
There are many ways to do this job, and this is just the scenario that goes thru my head when I do it. It makes sense to me, and it does work for me. Other people are very successful doing it a different way.
I still have a lot to learn, however, so you do what makes sense to you. Really wish you the best of luck, young fella, not trying to tell you what to do.

Just want you to have any information I might be able to provide.
Cheers,
K