They don't seem like they pose any issues in our systems.
"The reproduction of the smaller fireworms that are also common in our systems, in the genera Linopherus or
Pareurythoe, is less obvious, but they also can maintain quite stable and large populations in our systems. Most of the fireworms found in our tanks are in these latter two genera, and these animals occupy burrows in the sediments as well in holes in the rockwork. If not hassled by fish or crustaceans, they may be seen commonly during the day looking for food and doing their other wormy activities. These smaller species may reproduce more frequently by asexual than sexual means as indicated by the abundance of worms that are regenerating either front or back ends. As with the small starfish that are common in some reef aquaria, these worms reproduce asexually by fission, after which both halves produce the missing component." test taken from
here, reefkeeing mag article.