Mondo,
In our experience sponges are some of the most beautiful yet challenging species. Although air exposure is a huge issue, proper flow is key. Most sponges are collected at depth in areas of significant alternating current. The question here is were the sponges exposed to air at the collection facility? Few operations handle and hold sponges to avoid exposure. In our experience ball sponges fair the best. The more branching, the more difficult. There are some species that are photosynthetic but these are rare in the trade.
Good luck with your specimens.
Big Al's BC