Hi Ladyatlas, and welcome to the forums! Honestly, if you haven't gotten a reply, it's probably because no one who has read your post has come across the same problem or dealt with it before. If someone knew what it was, they'd certainly tell you. Especially something as strange as that.
Now, I can tell you that you should never totally break down a tank and boil and scrub everything because what you've done is killed any and all beneficial bacteria that had established themselves in your tank. It's like your tank is brand new now, and you're starting over. This is quite dangerous for the fish because it's like dropping a whole load of fish in a brand new tank, you're going to have an ammonia spike and every other problem associated with cycling a tank with fish in it. Do go to the stickies in the Newbie forum and read the sticky on "Cycle". It explains how a new tank establishes itself.
Now, that said, there has got to be a cause for this gunk in there, so please tell us the basics:
-What size tank is it?
-how long have you had it up and running?
-how long has it been since you did that total breakdown?
-do you have a test kit or have you ever had your water tested? Like at the pet store? To tell you what your ammonia level, PH, Nitrates, etc are? What are the levels at?
-how often do you do water changes on your tank? and how much water?
-do you use a gravel vacuum when you water change?
-how many fish and what kinds of fish are in there?
-how much, how often, and what kind of food do you feed your fish?
This info will give all the "old timers" on the forum something to consider and help them give you options on how you might get it to go away.
Thanks! And Good Luck!
