
Sorry you haven't gotten an answer yet. I've been just popping through threads today, and haven't really answered anything because I don't really consider myself an expert, yet.
I'm sure that if you wait for a bit longer, a few of the more experienced people will be on, later, and they will probably help you.
As for the little critters you've found...I'm not truly sure what they are. I know that it's difficult to describe some of the things one finds in their aquarium, and although a picture would be useful, it's not always easy to get one that's clear enough, or detailed enough to be of any use.
So, from my own aquarium stuff, I've little critters kinda like what you're describing. They've built little corraline tubes on some of the rocks in my tank. Their tubes appear to be very solid and completely white. A clear or white "flower head" pops out when they're not scared off by something. They appear to be a cross between a barnacle and a feather duster, and I've always assumed they're some sort of coral, but I've really no clue.
One thing I'd like to stress, though, is this. You have become an amatuer marine aquarist, like many of us here. Although it may be difficult, it is very important to be patient...a perfect ecosystem is not set up overnight, and an important question may take time before the "right" person (the one who knows what they're talking about) comes along to help out.
I've been "playing" with marine aquariums for almost 2 years now, and I've yet to have the "perfect setup". Part of it's money, part of it's time, and alot of it is that I make ALOT of mistakes.

But that's all part of the learning process right?
I'm not sure that I've helped out any, Indy, but I do hope that you hang around until you get the answers that you want. They are around here somewhere, I'm sure. But often it takes a bit more time before an answer can be found...