I was able to get it after closing and opening the aquarium a few times here are some pics (It's still a spoiler so I put it below):
It's kinda like the eggs from deltarune
yeah i just saw this too! i wonder what the meaning of it could be, since i couldn't get it again unless i could get to a new file. (i used the browser to get it again (it also spooked me at like 12:30 am 😭)
