I'd found most of those articles/threads before I registered here, so I never got to see the comments..  I should have another look.

I dug up some photos from two days ago of the fish with the black top and the purple in front of the tail.   http://canning.wemm.org/~peter/fish019.jpg and http://canning.wemm.org/~peter/fish030.jpg  They are a bit grainy, but you can see the black in these.

You know, I thought I wrote about the fish with what I now think was columnaris.  It struck overnight..  the evening before it was a bleached white patch, the next morning it was all white and fluffy.  At the time I misdiagnozed it as fungus and used AP's anti-fungus (malachite green + acriflavine).  It seems to have worked.  The fluff lifted off after the meds were started, exposing the (I think) raw flesh underneath.  NASTY!  Anyway, she started growing skin/scales back instead of dying and is now very active back with the main tank.

Now the timing of this is suspicious..  She had the white "bleached" patch while she was in a breeder net right next to the fish I was asking about in this thread.  They both should have been due about the same time.  Except the one with the black on top and the purple sides dropped her fry and was moved back to the main tank.  The next day the fluff attacked the second fish.  I dont like coincidences, but I can't help but wonder.. If it is the same thing, why didn't it attack the mother so viciously too?  Why hasn't it changed for two weeks, while the victim that succumbed was virtually shredded overnight?  I just can't convince myself that its the same thing.  Or if it is, perhaps it just hasn't got a good foothold.

Anyway, the fish that had the fluff outbreak is here:  http://canning.wemm.org/~peter/fish06.jpg - but this was about a week after the outbreak.  As you can see, she's healed quite a bit.  I have a more recent photo of her here:  http://canning.wemm.org/~peter/fish045.jpg - swimming with some other (presumably pregnant) fish.

On a side note, are the fish in that last link pregnant or overfed?  The top two are (I think) overdue.  I read that they can abort or delay a drop if they're stressed..

On another note.. notice how all their eyes are dark in the photos?  They look like that for real..  Some have normal eyes, but most are dark like that.  Should I be worried?

I read about the bird/snail/fish parasite problem, but it was talking about catfish.  I didn't realize that it affected these critters too.  I would almost be relieved about that possibility except that this article http://www.solodvds.com/digenetic_flukes.asp mentions a fish->snail->fish final (deadly) phase.  I think its time to kill the remaining ramshorn snails that the yoyos haven't caught yet.  The two problem guppies were in the tank with a major snail outbreak.

Yes, Mardel specifically says that coppersafe can be used concurrently with maracyn (broad spectrum gram-positive antibiotic) and maracyn-two (broad spectrum gram-negative), as well as maroxy (fungicide plus some anti-bacterial and anti-parasitic properties).  In fact, they recommend coppersafe in parallel with any of their other treatments in case parasites take advantage of a weakened fish.  They also say that when used at their recommended doses, that it shouldn't hurt the biological filter.  Well, I'll believe that when I see it. :-)

Yes, I'm doing very regular water changes (25% - 50%) and I'll re-add new carbon to remove any traces of medication before changing to something else.