Oh yeah, the original question.....
WHen I have a parasite out brake I do a few things. I like to do a decent size water change and vacuum the gravel bed very thouroughly. THis will decrease the population size of most parasites decreasing the severaity of the out brake. The idea behind adding salt to a fresh water aquarium as a parasite treatment is "iffy". What adding salt does is slightly irratates the fish so it will excreate additional mucas (thickening up it's slime coat). THis is good but does not kill the parasite, it makes it tougher for the parasite to be successful. This does work if the out brake is not major. A table spoon per 5 gallons is acceptable for most fish (you didn't mention what kind of fish you have) The salt will not leave your aquarium, even evaporation does not decrease the salt level. Water changes are what will remove salt in your aquarium. If you choose to maintain salt in your aquarium, only add salt after you do a water change and only for the amount of water that you removed and replaced. I.E. (you drain out 5 gallons and add 5 back, you add 1 table spoon of salt back to the aquarium). The reason it is often suggested to raise the tempeture is to speed up the life cycle of the parasite. In fresh water, ich or similar parasites have a fairly long life cycle, average about 14 days + or - depending on mostly the temp of the water. The life cycle goes like this.... THere are parasite cysts living in your aquarium all ways, nothing you can do to not have them. The cysts are fairly un active. When something triggers their life cycle to start, like a water temp fluctuation for example, the cysts grow into what is called a tomite, this is the free swimming part of their life cycle where they search for a host (your fish) to feed on. When they have found a host to feed on they fully mature, this is the part that we see, the white dots all over your fish. At this point they fall off, reproduce and the whole cycle starts over again. Each one of those little white dots can reproduce several dozen new ones. A minor problem can become a major one real fast because of this. The only time during this life cycle that the parasite is suseptable to medication is during the free swiming (tomite) part of their life. THis is why most parasite medications suggest to maintain the medication in the water for 14 days even if it looks like the parasite is gone. Most fish will be fine with a copper based medication like malachite green or similar. Smooth skin fish like most catfish or loaches or knifes are real sensitive to copper treatments so if this is what your dealing with be very carefull.
Back to what I said about the cysts all ways being in your aquarium, under ideal conditions healthy fish easily deal with the "bugs" living on them and in thier enviroment. Compair this to how we as humans will allways have the cold and flu existing in our world. When somethings happens to weaken our fish like poor water quality or diet for example, parasite outbrakes often occourbecausr the fish's immune system is not strong enought to cope with it. Likewise, when something happens to signifigantly increase the active population of the parasite, like a temperture change, even a healthy fish can be over come. Sorry this was so long a post, hope it helps with solving your parasite issue. If I can help in any way let me know..Joel
