white spot problem

[markfresh]

hi all i have had a marine tank for about two years and every now and then have a problem with white spot
i have tried copper in a quarintine tank and it seems to go away i leave the fish in quarintine for 2-3 weeks and after puting the fish back in the main tank it ussally gets white spot again.
it is also hard to catch fish out of my tank due to the amount of live rock
i have tried different coral safe and non coral safe treatments in my tank but it keeps coming back
i am aware of the white spot cycle and have left my meds in the tank long enough to kill the dorminet white spot . but a few weeks later
also i have 4 fish that i have had for ages that dont get white spot when the others do
any suggestions on remedeies and products
cheers

 

[coastal]

does your temp drop several degrees at night and do you have a sand bed?

 

[tangster1]

Have you tried a couple of cleaner shrimp--they've done wonders on ich with my tangs.
Tangster