You can use your HOB filter, just be aware you'll want to clean a lot more often than you do a FW set up.
Personally, I used a sump on SW and I use a sump on my 2 FW tanks right now. As far as I'm concerned, it's the only way to way. So much less maintenance.
You'll definitely want a skimmer. They make HOB skimmers (if you stay sump-less). Heck, even if you go with a sump, you can hang the skimmer off that. Remora Pro from AquaC is probably the best HOB skimmer out there.
Refractometers are probably the best way to test for salinity, but the plastic boxes with the swing arm arrow thingy work as well, and they're heck of a lot cheaper. The key is to make sure you rinse it out after every test because the salt can get caked on the arrow and mess up the reading because it can't move freely.
Personally, I used a sump on SW and I use a sump on my 2 FW tanks right now. As far as I'm concerned, it's the only way to way. So much less maintenance.
You'll definitely want a skimmer. They make HOB skimmers (if you stay sump-less). Heck, even if you go with a sump, you can hang the skimmer off that. Remora Pro from AquaC is probably the best HOB skimmer out there.
Refractometers are probably the best way to test for salinity, but the plastic boxes with the swing arm arrow thingy work as well, and they're heck of a lot cheaper. The key is to make sure you rinse it out after every test because the salt can get caked on the arrow and mess up the reading because it can't move freely.