Where have my sponges gone?

[CRAP! Another Hobby]

Up until a weekago, I had many many sponges growing nicely in my tank. Now all of a sudden they are gone. POOF...

I don't think it has been caused any water params.

I added 2 emerald crabs and a sea hare (or should I say "sea houdini") a week ago. Would they eat/harm the sponges?

[marie]

Sponges come and go depending on the nutrient levels in the water column. The more nutrients the better they thrive