If you do the salt thing just monitor for a week
Normal salt dosage is around 1 gram per litre or 4 grams per gallon.
You can go up to 3 grams per litre or 10 grams per gallon.
Raise you tank temperature to 30-32 degrees celsius (86-90 F)
Partial water changes every few days is good.
If you still have the rubbing issue, you more than likely still have some sort of parasite, and will need to dose with anti parasitic medication. From my experience with anti parasitic medication and arowanas, is that you never overdose the medication, and normally have to use follow up dosages to fix the issue.
when using anti parasitic medication, keep the tank temperature under 80 degrees F, keep the water neutral to slightly acidic, and dilute the salt out of the tank with normal water changes.
Once finished the anti parasitic treatment, it's a good idea to give the fish some antibacterial treatment for any secondary infection the parasites may have caused.
Usually salt treatment will surfice for this, or a treatment of cajut oil or similar will do. There should be need to go for the hard stuff like tetracycline.
Do you feed your jardini live feeders ?
