WTH is the micro-organism and why is it in my house?

Recently, as in the last two days, both kids have lost their 'sucker' fish.  Both died within a day or two of each other.  Both were bought at the same time along with Farmer, Jr.'s goldfish, "Aggie".  "Aggie" is fine.  "Rainbow" has done fine since we bought her this past summer.

So, a few minutes after fishing out said dead algae eater from FJ's little fish tank and tucking him (FJ) in, he comes back to show me 'what's this thing swimming in my tank'?  He actually fished it out and we videoed it swimming in a drop of water on his finger.  Ew.  Weird.  I'd load the video but my flip-cam is on the fritz (see previous post).

That's about the size of the, um, thing.  Here it his blown up for a closer look:

If you click on this you can zoom in even closer.  There are eyes, what looks like lungs or a respiratory system of some sort, a tail with like I don't know finny thingies, and fins on the side.  So, is this a cootie that got in the tank?  Or is it a baby 'algae eater'?  I've had little fish who've been pregnant when I bought them so I can recognize a baby fish.  They look like, well fish -- just really, really small.

This thing was wigglin' like an amoeba in that little drop of water on his finger.  But, amoeba's aren't visible to the human eye -- right?

Anyhow, I'm figuring it came from the local Wally-world where the fish came from back on FJ's birthday earlier this month.  Still, add that up to my list of things to do = change two fish tanks.  Just in case, you know.  Since both those littler buggers died.  And, one brought along this...  this... weird, funky, ewie thing.

Okay, a little bit cool.  Maybe 15%.  The other 85% ew.

Thoughts???

WTH is the micro-organism and why is it in my house?