So treat with paraguard no matter what kind of preventative? Does it contain copper? Can you give me a quick how to? Cycle, paraguard as on the bottle, fish. How many waterchanges per week and how much each time?
I'm not a big fan of medications like this. If you check the manufacturer's web site you'll see that they really do not tell you what is in the product.. This is from their website "...ParaGuard™ employs a proprietary, synergistic blend of aldehydes, malachite green, and fish protective polymers that effectively and efficiently eradicates many ectoparasites on fish (e.g. ich, etc.) and external fungal/bacterial/viral lesions (e.g., fin rot)....".
When I see this sort of questionable stuff, I think "snake oil" and that your best avoiding the product entirely. For medications I would consider using, depending upon the disease, see this thread -
http://www.reefsanctuary.com/forum/...cking-the-marine-fish-medicine-cabinet.23117/
As for treating fish on a preventive basis, yes this should be done in at least some cases. Many clows seem to arrive with clownfish disease. Tangs can often be 'ich magnets". Other fish seem to have less problems, so it more a question of how you feel about it.
As for water changes in a quarantine tank, almost any med that actually works will tend to kill of the bacteria base in the tank. You usually need to test for ammonia, and if you get a reading, make a large partial water change. Yep, you'll be running through a lot of water. Don't forget to re-add the med for the amount of water changed.