Originally Posted by asylumdown
Marine ich and freshwater ich are similar organisms in a lot of ways, but they're different species with different pathologies. It can go very quickly, as the parasites tend to build up silently over a couple of generations, then when their numbers are truly astronomical, your fish suddenly falls apart on you.
The one thing about it however, is that it never really "runs its course". If C. irritans is present in a system, and that system has fish in it, all the research and anecdotal evidence indicates that it will continue to persist. The existing fish will likely develop a partial immunity and you will likely stop seeing symptoms over time, but the parasite will most definitely still be there. If you search the various forums, you will find a variety of opinions on whether or not this is a problem, but the one thing that it will guarantee is that if you don't take the steps necessary to eliminate it from your tank, it will always be a gamble for you to add ich prone or delicate fish. Before my first and (thankfully) only total tank wipeout, I managed to reach a level of equilibrium with my established fish - none died, and very few ever showed visible symptoms. However, my rate of loss for new fish (especially ich prone fish like tangs) was around 70%. Even with a good QT and fattening up, a fish's stress levels are highest and their immunological defenses are lowest when they're first introduced to a new community, which is exactly the conditions ich opportunistically exploits.
Whether or not you can ever have an "ich free" tank, is a contentious point of debate, but you can go through steps to clear your display of it as much as possible. If your yellow tang survives and you put him back in an infected display that has not been run free of fish long enough to break ich's life cycle, you will very likely end up in the same position with that fish again. Over time it may develop enough of an immune response to cope with a moderate level of infection, but it will need to be in really good shape to do that.
The only way to let ich "run its course" is to remove all fish from the display, treat them all in a separate QT system using one the methods that are known to be effective (there's really only 4), and let the display tank run fallow for 9-12 weeks (depending on who you ask, I err on the longer side as it would suck to waste 9 weeks if it wasn't long enough).
The other option is to just deal with ich, a many on here do, which is possible long term, but you will always have problems adding new, stressed out, immunologically naive fish and may never have success with the more ich prone species. You will also need to maintain optimal diet and conditions for the fish that do adapt so the parasite never gets the upper hand. If that's the route you go, I'd still wait a couple months before adding new fish, having three fish kack it on you will have contributed a pretty significant number of encysted ich tomonts to your system. While you'll never clear it without going fallow, having the tank populated by ich resistant fish *should* mean that over time the "parasite bank" will deplete, as fewer will live to complete the life cycle. The less of it present when you do add more fish, the better.
|