my filtration

Whats your temp? Did they die quickly in a few hours or a couple of days?

 

Is this the worm you found?

I don't remember what these are called but they do cause problems when they get big. I caught this one a few months ago in my tank. I was up at 3:00am feeding my baby and took a look at the tank and saw this monster swimming around. I thought I was seeing things at first.
-Bill

 

If they're the greyish silver type of bristle worm, I don't think they're a problem. I have some large ones in my tank and they're just detritus feeders, sort of like large earthworms. If you handle them, you will get their bristles stuck in your skin and its irritating, but you'll survive /DesktopModules/ActiveForums/themes/_default/emoticons/smile.gif They are in most tanks and I see them as beneficial. That thing Bill had in his tank looks like a fireworm and I've heard they can be an issue. They're a type of bristleworm too, but are red.....

 

Posted By mthomp on 03/13/2010 12:59 PM
thats it, havent so much seen it swimming around to where i can catch it, it tends to keep inside of a cave in my rocks where i cant get to it.
any thoughts on how i can go about nabbing this guy?
I got lucky with mine it was free swimming when I first saw it and It was like 6 to 8in long I freeked and grabed some scissors and choped it in half then while it was squrming around in pain I neted the two halfs. If you know where it lives you could take that rock out and put it in a bucket with an inch or two of water in the bottum. Then maybe it will come out of the rock into the waterin the bottum. Don't know if this will work or not but might be worth a try.
-Bill

 

Unless its really big, I don't think they're a problem, in general.  HERE'S a good article about worms in your tank, if you have the time.....

 

She's right unless it is a big one it's most likely not what's killing your fish.

 

Ever check for stray electricity in the water?
Just a thought.
-Eric

 

As Fawn asked:
How do they act after you've released them into the tank?

Do they hide?

Swim near the surface?
Respirate quickly etc?

You mentioned:
"best example is i recently brought home a sixline and a firefin. i had a clown well established in the tank, come home from coffee today and the sixline and clown are dead but the firefin is doing wonderfully."
How long were the new specimens in the tank?
Were they fine when you left and dead when you returned?
Any signs of physical trauma/damage?
Is the firefin still alive?
Appears to me that something is being overlooked.  A 55 gallon is enough to support the number of fish you're introducing. 
Filter discussion being what it may, if you don't have ammonia/nitrites/nitrates/ph or alk issues significant to be toxic then it doesn't matter at this point.
There's either something in the tank/water that you aren't aware (chemicals/voltage/etc.) of or you have a predator that you haven't seen which it why I'm curious as to how the fish look after they've perished.
-Eric

 

Brooknella (totally misspelled) can kill quickly, but there would be signs (Google images). The things I noticed that may have had something to do with your fish dying were the long time you floated them in the bags (poor oxygen) and not drip acclimating them (especially the wrasse, they should be drip acc. for sure), although I would think they would have showed signs of distress right away if that was the case, but maybe I'm wrong. Your pH seems low at 8; is that WITH the lights on? If it's only at 8, I can imagine it drops down quite a bit lower with the lights off....maybe too much of a change from what the pH was at the pet store (or wherever you got them) for your fish. Ideally, I like my pH to be at 8.4-8.6 with the lights on. pH is an important parameter to keep steady, crazy fluctuations can be bad......something to consider, might want to see how much it changes in a days time.