To sponge, or not to sponge! That is the question.....

I've read a bunch about how sponges are really great filters and do nothing but good for your tank.  Reefs2go and reeftopia both offer a few sponges...are these ornamental types just as good for filtration as a duller gray kind?  And if its the "plain" sponges I'm after....and my live rock didn't have any, where do you get them?
I also read wildly differing things about how easy they are to keep....anyone have some experience to share?

 

I have a ton of pure white ones, they grow in my sump.

They do help with filtration, to what degree I do not know.

 

I just recently started noticing the 'dull grey sponges' growing in the caves of my live rock. I never intentionally introduced them to my tank and the current setup has been running since April to give you a time span of when they may show up on their own if your live rock was seeded with them.

 

I've never bought any sponges, they have only grown from the LR in my tank. Honestly, even though sponges are filter feeders, I really don't think they would do all that much for your tank. If you are going to get some though make sure they don't get exposed to air. Sponges have a difficult time expelling air bubbles.

 

I have been lucky. I have some bright yellow ones and some kind of encrusting sponge that is a dark purple.

 

I have yellow, pink, white, black and grey sponge. I do not know how good they are at filtration. My black and grey sponge love lighting whereas the others are on the underside of the LR. They should never be exposed to air. For the most part, they are very slow growing. I would not buy sponges for filtration purposes as there are other better methods.