Australian White Lightning Sponge - Turning Brown - Newbie

[ibizatunes]

Firstly I didn't order this (wasn't planning on getting corals for a few more months) only cycled my tank about 5 months ago, I order 10 Mexican turbo snails but this arrived in the box aswell, so I thought sweet free coral!! 

   - However its now starting to turning brown
 
Lighting - I have 2 max spec razor 10k lights and a 500l tank
Water reading today
Ammonia 0
Nitrite 0
Nitrate 5.0
PH 8.2
Phosphates 0.25
KH 9
Calcium 400
Density 1.0.23
 
Currently it has good flow of water, and is in the centre between the 2 maxpect razor 10k
I have try feeding it plankton and have coral food but that isn't stopping it from turning brown
Any ideas as i have never looked after coral before
 

 

[Donya]

Unfortunately, these sponge/polyp combinations are very hard to maintain. Even experienced reefers with established tanks tend to have bad luck with them long-term. Sponges often have problems with algae growing on them in reef tanks; could that be what the brown color is in this case? If so, put it in a more shaded area (the polyps do not need light, just food). Make sure not to expose the sponge to air when moving it.
 
EDIT: forgot to say that I am going to move this thread over to marine inverts.