I purchased a trigger ruby sump for my new 90 gallon saltwater tank.
So my question is:
Would a refugium be a good idea, for a fish only tank???
Refugiums are good if you have the ample amount of live rock in your display tank. Fuges are very effective at keeping nitrate levels down by growing macroalgae and certain "bugs" that also aid in the process.
They are also required if you plan on housing any type of Dragonett. Since they primarily feed on copepods. But some will take to frozen or even pellet foods.
The best way to use the fuge imo would be to have a deep sand bed using a 70:30 split of fine:coarse substrate. While at the same time growing chaeto or similar macroalgae. This method will allow you to grow the necessary various bugs to keep a successful fuge.
They are mostly designed for reefs a FO would not benefit from it much the fish are not effected from nitrates and phosphates this is what the cheato thrives on and helps to rid those areas for a reef tank, you would be better off putting live rock with a good venturI skimmer in the sump.