Algae ID

[jerryb]

This seems to fit the description of sargassum, brownish/green, lighter colored veins and what appear to be light colored bulbs at the center. My Mithrax crab goes out of his way to eat around it, as do the snails.

This has been developing on a couple of my live rocks (Fiji) almost from day 1. I am into my third week of having the tank going. I sped up the cycle by using Fritzyme. My params are amm=0, nitrite=0, nitrate=5 (and dropping). Calcium=460, alk=10.5, mag=1450.

[horge]

I can see the midrib and veins clearly on one blade :)
Fucales aren't my strong suit, but that sure looks like Sargassum.

Hard to tell what species until it gets bigger, but why wait?
In any case it is not quite an appropriate species for a tropical coral reef aquarium.

They likely got in, already on the rock.

hth