I saw some small blue sponge frags at an LFS a few weeks ago. They still had some when I dropped by this afternoon, so I got one. It was only $12, captive raised, just the right size for the niches in the sponge rock.
(Click for bigger picture.) This is a nice “group shot”. To the right of the sponge, Belle waves in the current. To the immediate left of the sponge is the usually elusive Drew the snail, and coming over the back of the rock on the left is Cali.
Keeping this sponge healthy and happy may (or may not) be a challenge. I did some research on it on the web. It’s Haliclona sp. It’s from the Indo-pacific or maybe the Caribbean since there’s a species of similar blue sponge there. This is the most minor of the contradictions I found online. It requires low to moderate light: it need intense lighting. It’s photosynthetic; it’s not photosynthetic. It easy and requires no additional feeding: it’s extremely difficult and must be fed commercial plankton preparations 2-3 times a day….or…It can only digest natural plankton and will die if fed commercial plankton. It’s toxic to humans, fish and corals and is not suitable for a a reef aquarium: it’s an excellent addition to a reef aquarium, totally benign and peaceful, cleaning thousands of gallons of water per day. So, I’ve either just acquired a doomed problem child or a real star. 
The only thing all sources agree on is that it requires good/high current and must not ever be exposed to air, both of which are true for all sponges.
Prior to introducing the sponge into the tank I cleaned the glass, removed a small patch of cyano, ripped off some of the algae on the Fiji rock and did an approximate 2 gallon water change.
I acclimated the sponge over a 5 hour period, then placed it into a niche on the sponge rock.
Tested the Ph at 8:12 pm. It was 8.1.
