he has an adipose fin, although it is hard to tell for sure since he is so small and his fins are still clear, so I suspect he is some type of Characin. When I first found him he was smaller than a Guppy fry is at birth. I noticed him because of his eyes, he has bright blue eyes. His body still hasn't gotten adult coloring yet, but it seems to me like the blue on his eyes has just started spreading to his forehead a little. The rest of his body is almost clear, slightly cream colored like many very young fish are.
Here is the best picture I could take of something so small. You can at least see the shade of blue that his eyes are.
I'm exceedingly puzzled by this because I use separate equipment (nets, hoses, etc) for all my tanks and always wash my hands between handling them. I assumed at first that he got in from my 75 gallon as an egg and hatched in there, but he doesn't really look like any of the fish in the 75 gallon - which are Praecox Rainbows, Harlequin Rasboras, Gold Tetras, Panda Cories, and a single Bristlenose Pleco. But of them, only the Praecox have blue anywhere, and their eyes are not blue, and the blue is a different shade than the fry's. And the blue has only gotten stronger in the fry as he has gotten older. I added some Taiwan Moss to the shrimp tank a while ago, but I did use Potassium Permanganate to disinfect it...I'm now thinking that maybe part of the moss was out of the disinfectant bath and the egg got in on that and then hatched in the tank, in which case it could really be anything.
I found the fry on the first of May, and have since gotten very attached to him. I had been feeding him Hikari First Bites until I was able to find some liquid fry food. Right now he's eating mostly liquid fry food, but also some First Bites for variety still, and I have a culture of Brine Shrimp that should be ready for him very soon. I'm feeidng 3-4 itty bitty meals a day. I removed him out of the shrimp tank as soon as I found him because I wasn't sure when he would be big enough to eat my 1 mm shrimplets and didn't want to find out the hard way, right now he is in a large plastic guppy breeder floating in the 75 gallon, the kind that lets water flow in and out. I clean it out periodically so uneaten food isn't lying around, but he has the full filtration of the 75 gallon to keep the water quality good. He's growing slowly but well, and seems to be doing better once I got the liquid fry food, he's more colorful and growing faster on it. Hopefully I didn't stunt his growth by feeding that Hikari stuff, which I strongly suspect is just crushed up flake...is this treatment okay, or should I be doing something else?
I'm really curious to see what he is. I'm hoping he'll be compatible with my other fish and that he'll be a fish with a low enough bioload that I can get him a little school once he's grown. I'll probably ask here if that won't be overstocking once he's big enough that I am absolutely positive on what type of fish he is.