You forgot to post a pic of it. It could be anything without a picture. Maybe it's an ant or mosquito or poop or frozen peas, maybe a cucumber that's gone bad or some tree bark. Get the picture ( no pun intended. )Why is there black stuff in my aquarium sand? Is it poop, or food? should I clean it? This is in my 40 gallon tank.
Well that's definitely no fish poo. Did that happen all at once or has it been building up?here is a video of the black stuff in my tank.
Okay. Yes, siphon it all out. It's most likely algae but I saw in your film a piece waving that could be a piece of flake food. One of the things about using sand is that things will gather on top of it more than if it were say, gravel or pebbles where things would grow in between the pieces.been building up. Should I clean it?