It will not help ich . Not much else to say. Dallying with it in lieu of an effective treatment cuts the odds for your fish to survive. .
There is a new ich elixir hitting the market every 6mos or so. Sales benefit from the natural placebo effect ; some fish naturally survive less virulent strains of ich and some develop partial immunity wtih or without the elixir. Some survive the first infestation and succumb to a more massive outbreak later.
The only proven mainstream treatments for cryptocaryon irritans are: copper, hypo salinity and the med free tank transfer method ; hypo fails often,ime and won't do anything for velvet( amyloodinium).
The ich parasite is an equal opportunity killer, it attacks healthy and stressed fish whether they are well fed or not.
Copper is very effective against both ich and velvet at therapeutic doses.. Copper sulfate does suppress the biofilter sort term ,about 20% according the the manufacturer of the product I've used . Bound copper medications less so. I've used copper sulfate as well as cupramine many times without ammonia spikes or fish deaths and have saved fish from ich reinfestations with it.
Alternatively removing the fish and providing tank transfer treatment for ich works very well and is med free. FWIW it is the method I prefer. It involves using at least two tanks with gentle transfer of the fish every 3 days for 4 transfers. All of the parasites in the fish leave within three to seven days and take 3 to 28 days to go to the bottom and form new attackers. This method simply leaves them all behind with no fish to attack until the tank and equipment is thoroughly dried which kills them at any stage in their life cycle.
The tank needs to be left fishless for 72 days as some tomite cysts have remained viable for that long in one study . Most likely 60 days or even less would eradicate them but 72 is safer. If it's a fish only tank a copper treatment with carefully monitored levels and ammonia monitoring could work very well faster. However, the rock substrate and other items in the tank would not be safe for use in any tank housing invertebrates due to residiual copper.
FWIW it is the method I prefer. It involves using at least two tanks with gentle transfer of the fish every 3 days for 4 transfers. All of the parasites in the fish leave within three to seven days and take 3 to 28 days to go to the bottom and form new atackers. This method simply leaves them all behind .
