Hi, you may wish to check with LCk or Iwarna on NSW top-up for your tank setup. It does help to speed up cycling. Thereafter on water change, it will depend very much on you...salt mix or NSW. For the skimmer, you can consider out-sump skimmer if you have space constraint in your sump. FOr Hang on type, the skimmer cup is usually small unless you modify. Just take the dimension allowed for skimmer and look out the various suppliers to determine which to buy. Do take note on maintenance space. For skimmer, Deltec, Bubble King, New Series Reef Octopus, H&S, Skimz, etc seems good but check out the after sales service. All the best.