brstle worms

[Jazmine18]

How large do bristle worms need to get before they are considered bad for your tank? or does not matter?

 

[greenbean36191]

Size doesn't matter. What type of worm is what makes the difference. Harmless fireworms are still harmless if they're 2 feet long. Eunicids and Oenone can be trouble even at fairly small sizes.