Bristleworms are actually beneficial to our aquariums, though many people would immediately think otherwise just by looking at them. The worms eat detritus and left over fish food, preventing them from decaying furthers. Bristleworms are usually a few inches long, often showing colors like pink/red or black. Occasionally, populations of these worms can explode, causing quite a bit of alarm to the aquarist. They can be removed through a variety of techniques, with a little bait being a very effective tool.