...I find it worrying that everyone is adjusting salt to treat ich on clown loaches.
Salt can be very good for some types of fish, on others it does nothing to their health, and on others it can have a very negative impact on the fishes health, even being lethal.
Most fish which can tolerate salt well have a certain level of salt found naturally in their habitat. For clown loaches this is not the case at all, and so clown loaches have not evolved to tolerate it well. Using salt to treat clown loaches for anything is very stressful for them, it puts a large strain on organs evolved to deal with salt and in higher enough doses salt can easily kill clown loaches.
Clown loaches are particularly prone to ich as they have little immunity against the parasite. You should always quarentine new clown loaches since they are so prone to getting it, and treating an entire community tank can be a pain in the bum. You should always make sure the quarentine tank is kept constantly cycled though, or at least clone some filter media before you put the loaches in, as introducing new clown loaches to an uncyled tank is very stressful for them.
For treating whitespot on clown loaches, i would advise using non-salt meds for example like "Anti whitespot" by Interpet.
Info on Ich;
1) Ichthyophthirius multifiliis ("Ich" or White Spot Disease)
A. The largest protozoan parasite of fish. The trophozoite are
up to 100 microns diameter, ciliated and contain an oval
horseshoe shaped nucleus.
B. This is a disease of aquarium and hatchery reared fish.
C. Clinically fish become hyperactive with fish flashing and
cutting against rocks or sides of aquariums. As the
trophozoites enlarge they cause hyperplasia of the epidermis
with white spots forming on the skin and gills. Severely
infected fish may have respiratory problems and die.
Histologically there is epidermal hyperplasia with the
encysted trophozoite present in the epidermis.
D. The life cycle is direct. Encysted trophozoites (trophont)
leave the fish and settle to the bottom of the tank. The
trophozoites (tomonts)divide into numerous tomites (theronts)
which are released to infect the skin of the fish. The life
cycle takes approximately 4 days to complete. However, it
can be sped up by increasing the water temperature.
E. The only way to treat the disease is by interrupting the life
cycle of the parasite. Removal of fish from the infected
water for 3 days (25øC) will usually interrupt the life cycle
(Tomites live only 48 hours at 26øC). One must treat the
water to kill the tomites to prevent spread of the disease
(Malachite green, formalin, methylene blue, or KMnO4).
Remember, these treatments only kill the tomites and not the
trophozoites that are encysted in the fish.