Assistance with sponge ID

[tinyaquatickiwi]

I acquired some rubble rock from the LFS a few months back. One piece of rubble came with 2 very interesting sponges. One is encrusting, purple and doubles in size about every 2 months and the other is transparent white and is about the size of a quarter. I figured they would likely die off but have been growing steadily for the last 6 months or so. Some help with IDs would be much appreciated.

 

[Ron Reefman]

Sponge ID's are very difficult at best. There are so many species and very often there are 2 or 3 different ones that look exactly the same they can only be ID'ed under a microscope or even DNA testing.

I love the look of the purple sponge! Does it grow out in the open and in the light or is it more on the underside of the rock?

BTW, are you in New Zealand? Is the rock you got local to you?

 

[oneofmany]

Maybe these links will help.

http://reefkeeping.com/issues/2005-06/rs/index.php

http://reefkeeping.com/issues/2005-07/rs/index.php

http://www.advancedaquarist.com/2011/6/inverts2

 

[Ron Reefman]

oneofmany, excellent links, thanks.