I know there is a lot of things we can buy that are not exactly needed, but def. help. I'm wondering besides your main things for water quality and just making your tank run( I run a basic loop system, skimmer, fuge/sump, and return). What else is money best spent on? I have been out of the hobby for 3-4yrs but before did run carbon in just a bag in my wet/dry filter and always seemed to work. Another reason for asking is I'm starting to plumb up my 125gal and want to make sure not to leave something out that might help out.