ANEMONEBUFF":1pgft0ic said:
Plus I believe that some of the white sponges are calcareous. So they eat calcium as well.
You can't use color as an indicator of calcium uptake. Sponge tissue color is often quoted as being an indicator of depth (drab colors are deeper), reef safety (brighter colors are better), calcium/silica/etc. uptake, methods of reproduction, etc. However, the sponges don't seem to agree with many of these classifications. There's simply too much variety in the family porifera.
If you want to know if a particular sponge uses calcium for it's internal structure: cut a small sample of the sponge's tissue with a razor, and crush the sample between two gloved fingers. If you can feel it crack and pop, there's a 90% chance that what you're breaking are calcareous spicules. Almost none of the sponges that use silica for internal structures are found in the aquarium industry. The notable exception is the Venus flower basket, though not as popular as it once was.
In any case, I personally love sponges in my system and am aiming for a skimmerless system where the sponges in a dark sump do most of the filtration for the system ala Steve Tyree's writings and test tanks. When sponges grow in the main tank, I'm usually thrilled, though I can see why some might be worried about having an aggressive sponge encroach on corals.
As an idea for
Jandree22, you may be able to look up Steve Tyree (
http://www.dynamicecomorphology.com) and see if he might be interested in cuttings of your sponge. Another fast-growing aquarium surviving sponge may be quite useful for those of us trying to find more natural filters for our tanks.
Regards,
Ross