Hello, yes you can use a protein skimmer without a sump, they make hang-on- the- back models. If you wanted to, you could also use the standard filter that came with your tank package.
From what I have read, in order to have the benefits of a deep sand bed (DSB
) it needs to be four inches.
I would recommend making the saltwater yourself using and RO
unit. These units remove impurities from your tap water. The water that you make should go right into a bucket, where it is to be heated and mixed with salt for about twenty-four hours before use.
Hope this helps.