Some sort of sponge? ID help needed please.

[targaboy78]

Hi gang,

I picked up 200lbs LS and 200lbs LR about 2 1/2 weeks ago and my tank is still cycling. These things were on the rock when I put them in the tank. Originally, they were flaccid (looking like silly string) but now they seem to be thriving. (I say thriving because they are growing and reaching towards the light - but what do I know... maybe they are trying to escape?)

Parameters;
Temp: 80F
pH: 8.1
SG: 1.024
NH3: 0.1 mg/L
NO2: 0.1 mg/L
NO3: <5 mg/L

I am thinking they are some sort of blue encrusting sponge (Haliclona sp. ?) In the bottom of my photo (six o'clock) there is a patch that resembles the Haliclona sp. on page 334 of The Conscientious Marine Aquarist. However, these sponges encrust rock and nowhere can I find a photo of one branching out.

OK, now my questions;

What are they?
Are they good or bad? I like the color and wouldn't mind keeping them.
If they are bad, what should I do next?

TIA,

Paul.