Yes there are saline tests--he needs to get one ASAP-and also needs to get a fresh water testing kit--check for Ammonia,nitrites and nitrates(this can cause flashing,gasping and death) so always check water parimeters first..If he has high ammonia or nitrites he needs to do massive water changes-stop feeding and get that water good again....bad water quality can also cause a parasite out break..If he checks the water and all the test are good then he probably has a parasite...by all means if he has access to a microscrope he needs to scrap and scope..if he doesn't he needs to get all the salt out of the pond by 25-50% water changes untill he knows the pond is free of salt because if its a parasite the meds don't mix with salt--it can kill the fish if salt is present.....after he is sure the pond is free of salt--he can use proform-c then on the third day of treatment--mix prazi with the pro-form C(shake it up in a glass jar or water bottle-you have to shake it like mad-litterally untill you don't think you can shake any more)add to the pond and leave that in the pond for 7 days..on the 7th day he needs to do a large water change..then the proform-c treament again--again on the third day of treatment add prazi again and leave for 7 days (this is a shotgun treatment and should get everything).....This being said I don't want to advice shot gun treatment unless its impossible for him to get a scrape and scope--Scrape and scope is always best but, when you don't have that--then shot gun treatment is about all you can do.....this should kill any parasites present....
Lawanna