sea lettuce and chaeto

I just purchased new bali rock for my new tank. It came with "sea lettuce" (ulva fasciata)

alive and well, my Marine plants of the Caribbean field guide says it "grows in high nutrient areas (e.g.mangroves, bird islands)". Can I assume it will help with nitrates? Is there a particular fish that likes to eat it?

The rock also came with chaetomorpha crassa,
on this board is this what people call chaeto, or are they refering to the smaller linum?

 

this is what we call chaeto

 

yes it will help to eat your nitrates. and some fish will eat at some of that stuff, so it usally goes into the sump

 

I have both Chaeto and Ulva (sea lettuce). It grows very fast like chaeto (even faster in my case) but you can feed it to your algae eating fish.