What are sighns of flukes or internal worm/parasites! With flukes, fish will usually be flicking against objects in the tank, usually by their gills. With internal parasites, fish will get skinny, usually excrete white or clear stringy poop, but it really depends on the type of internal parasite. / If fish had velvet for 6 months or more would it be dead by now!!, What are the symptoms that your fish have? / How much water should be changed per week in 180 ltr-i was doing 50 ltr per week-!!!,That's fine; That's about 25%.Keep up the weekly water changes. / Does pete affectively reduce hardness/ph!!, Yeah, it does. Keep in mind, it turns water slightly brown. / Does pete and bog wood/drift wood have to be removed when using meds!!, Bogwood/driftwood does not need to be removed during treatment. And for peat, I'm pretty sure it doesn't need to be. Cheers.