I still work with chemical combinatations to treat our koi," when I need them which isnt often" .
I think the last time I used a treatment was Fluke M after an outbreak of flukes sometime ago now interestingly all pond have parsites but fish are unaffected by hem until a chink appears in their armour [which the parasites will ruthlessly exployt.
I reality the best treatment is salt but you have to remember that it will stay in the system until water changed out .
Your Ph is dangerously near the 8.5 that if you had salted prior to treating with Malachite and formalin and not removed it then you would find that the formalin would become toxic .
If you must use salt I would say do a salt bath to remove parasites its the original treatment we fish keepers first used and it will temove parasites en mass, however I cant remember the ratio of salt you need to do a salt bath off the top of my head as its 03:59 am and I'm tired.
Your lucky in the US as you can use treatments unavailable in the UK or like Dimlin powder banned outright from the UK .
Not really. The only real UNIVERSAL TREATMENT is prevention -- keeping your water clean and monitoring water parameters. Healthy water will make your fish strong and help them resist diseases.
Fish diseases are like people diseases, and even a "broad spectrum" antibiotic won't get everything. That's why doctors do microscopic exams, or cultures, so see what antibiotic will work best. Or with most diseases, they go by signs & symptoms.
And, using antibiotics [or other disease "fixes"] indescriminently will cause other disease-causing organisms to become resistent to that drug -- which means, it won't work against the bugs you want it to fight.
So, when we treat fish, it's important to KNOW what you're treating -- and with fish we have to go by
Close observation is vital -- watch for DIFFERENCES / CHANGES!
Is it one fish, or multiple fish
have there been recent changes such as recent rains, temperature changes, etc.
have you added new fish
and I'm sure there are more, but that's all I can think of right now.....