So this mystery fish appeared in an uninhabited planted tank a few weeks ago, and I though it was just a figment of my imagination, since nothing has been in here since some bolivian rams spawned almost 6 months ago. Just plants! All I've added to the tank since then, is moss from a shrimp tank, some blyxa japonica that was dipped in PP and H2O2, and some assassin snail babies.
So I'm thinking it must be a killie of some sort, or maybe something else. It looks a bit like my golden wonder killies, but they've never touched that tank (nor have I used a net between the two tanks.
So I went to take pictures of this mystery fish, and i moved a piece of java moss, and 5 of them shot out, they are VERY shy, and do not like their picture taken. Right now they are about 1-1.5cm, and they haven't grown much in the past few weeks.
Here is a picture of one that I got to stand still for half a second while I snapped one off: