Len":2jxm9ici said:
Living sponges are harmless.
Not always true. Mind you, for the purposes of our tanks, 99.99% of the time it's true.
But some sponges can do some really, really nasty things with toxins. I remember reading a report about 8 or 9 years ago about a group of researchers who had a large sponge (several feet in diameter) in a tub tank of barely larger dimensions than the sponge itself. Over the next few weeks of working with it several of the researchers developed a condition similiar to aphasia - simply from physical contact.