Right now I have just a hob filter running carbon and phosban. I am going to get an AC30 to run even more carbon. Should I add a skimmer? Are there any decent HOB skimmers? Does my tank need any more filtration? I want to keep SPS in the future and I need advice.

why so much carbon? i just set up a fluval edge 5 gallon tank and i think it had the same filter your using but i scraped that filter and drilled the glass and made a 3 gallon sump i also have a skimmer rated for a 24 gallon only have 1 fish with his pistol friend 1 pom pom crab and 2 cleaner shrimp i feed 1s a day. do a water change of 4gallons every week i only dose with purple up seven drops of it all reads zero mag is @ 1380 ph is 8.4 alk is 10.0 .i drain all the sump water and 1 gallon of the tank water .i have miracle mud in the sump along with cheato im lookin 4 a small mangove tree 2 plant but not season 4 them i guess couse i cant find any.i have sps and lps and leathers .so try 2 do a sump if u got room your possibilites are endless with it skimmer doser what ever you want.

So could I use the AC30 as a sump?

Thanks

for a tank that small just do 50% water changes a week to keep the water clean.

there are only so many skimmer that would fit in your tank. almost all either will take up too much space, or work like crap

You don't need a skimmer.