Correct, no visible worms or deaths in the fry tanks at all.  However, the're voracious little things and it wouldn't surprise me to lose one and have it become lunch.  :o/

My thought would be to(I know this sounds a bit nuts, but I'm hoping that your statement of 300+ fry is an exageration.) divide one of the ten gallon tanks in half, and move the other fry into this one.

Nope, 300+ isn't an exaggeration.  But I haven't actually counted survivors recently, that's just the count of live fry I've removed from the main tank to the fry tanks over the last ~3 months.  With that number I could lose a handful and never notice.  In fact I pulled 8 more fry out of the adult tank yesterday.  I've got one tank for small fry, and one for fry large enough to think newborn fry are snacks, so I can put the adults in with the larger fry without a problem.

Then I would move the remaining fish into the other 10 gallon tank so you could flush out the twenty gallon as the Inkmaker suggests.

::nod::  

Before moving the sick fish into the ten gallon tank, however, remove ALL of the gravel, plants, and any decorations.

Ah, something worked out for the good!  There aren't any gravel/plants in the fry tank  :)  I have one plastic plant "mat" in the "little fry" tank, but the other is completely unadorned.  I really only planned to have one aquarium, but I just can't leave the fry in the tank to fend for themselves!

I know this sounds like a lot of work, and you might be thinking I'm from a different planet right about now.  But, there is a method to my madness.

No, it makes sense.  I just don' wanna (I'll do it, but I'll whine and bitch a lot in the process).

<snip>

Oh, BTW, Happy Mother's Day, and please don't hate me.  You can always choose the option to ignore me. ;o)

Oh... someone picked up on my bitchiness.  LOL  Sorry.  :o/

I don't have any reason to hate you or ignore you!  Well, unless I'm just an irrational witch, and I can see how one might come to that conclusion.  :o/  Thank you for the suggestions!

Happy Mother's Day to everyone (even if you don't have kids, Happy Sunday to you).  Thanks to everyone forr all the advice & help, and I'll mark my calendar & try not to post during the first week of the month from now on!!  ;o)