I brought up the link because you stated, "my plan is just a fowlr
tank maybe ill just make the salinity from 1.009-1.013 to prevent ich and other diseases." In my link I state, "In order to eradicate the parasite naturally the salinity must be <16ppt (<1.009); otherwise, lowering the salinity is pointless other than therupeutic osmoregulation." Regardless of ich, lowering the salinity does nothing more for the fish health-wise nor prevent disease/parasites. Keeping the salinity within a given range of their natural salinity is best ime. I would not perform hyposalinity in your main system as it will destroy any invertebrate life.