My old tank was over 20+ years and I had bristleworms and welcome them to my new tank. They are part of the circle of life and help breakdown the crap in the tank....now fireworms are another story.
Did yall see this....
fantastic research from this girl/woman hope she stays in the industry and helps our environment.
https://www.npr.org/2014/07/20/333192387/sixth-graders-science-fair-finding-shocks-ecologists
sailfin fish like to swim and love a longer more rectangle tank....so my 2 cents is that your saifin will be unhappy. I have two and they are always swimming back and forth and in and out of the rocks.