Coralline Question

[dare2dv8]

Can someone tell me what the benefits of having Coralline in my tank are? I have lots of it, it's spreading on to new rock I've introduced and I have an Urchin that likes to mow it down. Is it more of an aesthetic thing or does it actually provide something to the system that's biologically beneficial?

Also, I'm a little confused because I've been dealing with my phosphates being a little high but I've been reading today that coralline doesn't grow when phosphates are present in elevated amounts. I'm using a Nutrafin test kit with the results coming in at 2 mg/L. It's the only test kit at my lfs so I don't have the ability to cross check with a different test. Doing weekly 10% water changes + a couple of 20% thrown in for good measure don't bring the levels down. I don't believe I'm over feeding and I've tested the water source which comes out at 0 for phosphates.

Sorry two questions here which makes the title a little misleading.