If you can recognize a carrot sprout, you can also know if one has accidentally grown in your aquaponics. A carrot is a root vegetable. This means that it grows under the ground. When they are ready to harvest you have to pull the whole root out of the ground.
Once the seed sprouts, it will start to get bigger every day. Eventually, that blade of grass will start to resemble a carrot top. If you have seen a carrot before, you know that the top has frilly edges.