Zebra Danio Fry - possibly 1 fry?

Question

Last night while I was feeding my Zebra Danio's I noticed something extremely small was swimming in a Vertical position at the top of the tank.

On closer inspection it had a dark (what I assume head) & a silvery body. Before I had chance to get something to transfer whatever it was into, it had disappeared. It was only 2mm long when I saw it.

Does anyone have any ideas. It is a closed tank so nothing else could have gotten inside, but I cannot see any evidence of Danio eggs or fry anywhere.

Answer 1

No, I have had Zebra Danio fry hatch without any special care on my part, in my 28 gallon with 22 guppies (3 grown, 1 month-old fry and 18 week-old fry), 1 male betta, 3 Giant Danios, 3 Zebra Danios, and 3 neon tetras. Then I take them out and feed them crushed flake. They stick to the glass, but are capable of swimming if frightened. i have had them grow to where they can't stick to the glass anymore, then inadvertently killed them by mistakenly adding nitrate neutralizer instead of AquaSafe! LOL. i just found one fry and hope to save it.
Hope I helped!

Answer 2

No, I have had Zebra Danio fry hatch without any special care on my part, in my 28 gallon with 22 guppies (3 grown, 1 month-old fry and 18 week-old fry), 1 male betta, 3 Giant Danios, 3 Zebra Danios, and 3 neon tetras. Then I take them out and feed them crushed flake. They stick to the glass, but are capable of swimming if frightened. i have had them grow to where they can't stick to the glass anymore, then inadvertently killed them by mistakenly adding nitrate neutralizer instead of AquaSafe! LOL. i just found one fry and hope to save it.
Hope I helped!