Those damsles are not easy fish to capture either. I would definitely take them out (if you want to add other fish later) before you add any LR
to the tank.
Not to sound mean but you really need to do a lot of research. It sounds like you are getting some horrid advice. Also, are you saying you have a crushed coral substrate? That type of substrate and the wet dry is going to require LOTS of maintenance. FO
tanks can take higher nitrates but you may be biting off more than you can chew.
Also, you will definitely need to do bigger water changes (as has already been stated). We are talking about 24 gallons per week or 48 gallons every two weeks. No kidding.
Scrimp on maintenance or water changes and 6 months from now you will be wanting to sell that tank in a garage sale.