anarobic bacteria bubbles....

I'm thinking this might be the mystery problem my tank went through last month.... can anyone explain the deal on them?

whoops.....sorry, thought you guys already knew.....
I had a major problem last month that resulted in losing my angel, my ram, a few pandurini's and some cories and almost my rainbow shark from my main 55 gal. Before I realized I was up against something much bigger than a passing "ich" infestation, a lot of my fish had died. I was originally blaming the new additions of the pandurini's but was a little insecure at that idea. I do remember though that during the last couple of water changes, during the gravel siphon, there were plenty of bubbles coming up from the stones. I dismissed it, thought nothing of it until I started hearing about these anaerobic bubbles. I've never heard of them before in all my years of fish keeping. Before I lost anything else or what was left, I moved the rest of the fish over to the other 55 and moved those already there to a 30. Reason being that I did a double transfer is because of the sizes of the fish (a pleco who's 15"). The only one out of the bunch that looked as he might've suffered was the RTS, but he quickly recovered once removed from the tank and placed in the new one. For the past month I've been keeping an eye on the tank and this past week I moved over the pleco and some cories to test things out and all seems ok so far. I'll keep things like this for a week or so and try a few more...... so, it's been quite a month in the tank for me..... still can't get over losing that angel....

ok.... so I'm thinking of removing the UGF from the tank. It covers about half of the bottom. Is there a safe way to do it besides emptying the whole thing out?

(btw, am moving the fish back to the other 55 for the process, the lesson was already learned)

hmmm........about 2" on top of the plates, and where there aren't plates, I guess about 3".... it makes a difference?

the UGF plates.....I'm thinking (or so I read elsewhere) that using them might have been a contribute to the AB........ so I'm thinking it might not be a bad idea to remove it anyway and with that in mind only weighs heavier on the idea...... would I have to tear the whole tank down to do this as it may be easier and easier to recycle than to deal with what's under it? Or would I be able to do this safely while leaving everything as it is, removing the fish beforehand of course.... what do ya think?