wow, thank you!
I google hidden cup coral and positively id'ed it as Hidden cup coral (Phyllangia americana). Thanks for the tip!
I even just spot fed it so baby brine and it loved it!
If your correct about the sponge (very possible as the live rock is covered with several different types of sponges) I am just blown away by the live rock vendor. The rock I bought was $4 a pound and I received (upon request) 2 huge peices with the largest being 19" long that included:
a 4" brain coral (which all but died as it was shipped in wet paper towel
such a shame but about 15% is still holding on and seems to be growing back)
covered completely in several different shades of beautiful coraline algae, several different color flat sponges, foraminiferans and halimeda.
several types of fan worms (feather dusters)
about 9 large bi-valves (again, only 2 survived transport in wet towels however, phew they stunk!)
a bright orange box/ball sponge and one bright red tree sponge. Amazingly the tree sponge seemed to survive the trip. it became white on the outside a little the first couple days but seems to have regained it's deep, rich red color after 4 weeks in the tank.
The second peice was about 13" long and almost completely hollow with a tunnel going through it that my shrimp love and now add to the list 3 Hidden Cup corals.
55lbs shipped for $220
I don't know what the policy is about referring vendors so I won't post anything but if anyone wants a reference just send me a PM.
I've uploaded the picture he send me before I bought it and a second in my tank!
thanks again for the help with the ID!