Don’t worry, it’s not a fungus That dark brown stuff is all the vitamins and curcumin. As with any natural product, this sometimes differs per bottle, some have more and others less. But to be honest, we (almost) always have it here with every bottle. That is why we always shake them ourselves before use. You see it especially when the bottle has stood still for a long time in a cool environment. But seeing this is quite normal. Just like with a juice or smoothie, you will also see this when it is not used for some time.