What is this and what do I do about it?

[vetteguy53081]

So the tank is fairly new, was cycled with live rock (from gulf live rock), nitrites and ammonia were 0, nitrates 4.6, ph is 8.18.

We added 3 corals and 2 cleaner shrimp Saturday, and today I noticed this:

Prior to the additions the tank was spotless. The corals were dipped before they were put in the tank.

Diatoms and normal with a new tank until it has fully cycled and stabilized and can even appear with aged tanks. Wipe with sponge or magnet cleaner. Some snails like astrea and margarita will consume some