they look like dark brown clumps. If it goes in the water the poop might break down and just turn the water cloudy so you should change the water then. It wouldn't hurt to get your new pacman a 10 gallon tank, but at this stage the plastic tank would be fine. As a little guy they might hop around here and there but as they get older and bigger, they become sluggish and just tend to sit there (ambush predators). Just make sure the water level isnt too deep because they cant swim. I have many pacmans and they are alot of fun!