Here is what pegasus said to someone else with a white spot problem...
We realise you must be stressed out at this time.. but you need to understand that there is no "overnight cure" for white spot.. and moreso in the case of treating cold water fish.
To understand the cycle that the white spot goes through see here....
http://homepages.paradise.net.nz/grumpy ... 0cycle.htm
We can see that in the first stage that the fish gets infected.
This can be due to all manner of reasons.. from stress to chills.. to being run down.. or through the introduction of other fish, plants, or anything else that could hold the parasite... even a single drop of water from an infected tank can pass it on.
Once these little pests get on the fish they start to feed, and will stay on the fish until such times as they are full and ready to drop off.
Heat will speed this process up... but at 21C this could take quite some time.. perhaps a week or more.. and "nothing" you pour in the tank will kill it off.
Once they are full they will drop from the fish.. but during this time they are removing all the energy and stamina that the fish has... so the quicker they are removed the better.
Once they leave the fish.. then THIS is the ONLY time they are vunerable to any medications.. so it is at this point that you need to get the treatments going.
Because these parasites drop from the fish, they are now able to reproduce very quickly, so the more of them you can remove through water changes the better.
Siphon the gravel to do this, and take care to dump the water in a safe place.
If you hit them at the right time, (when they are off the fish).. then you should erradicate them.
Now, go and eat a whole family block of chocolate to calm yourself