didn't seem like anyone else has explained so
Ich
or Ichthyophthirius multifilis is a protozoa that has a simple life cycle. it is present in almost everyones aquarium, you as a fish keeper are helping to prevent it by maintaining good water quality and a stress free environment. By doing your water changes you ensure that the fish maintain a good healthy coat of mucus which protects them against Ich.
They reproduce by ejecting tiny capsules into the water which divide and form 1000's of white spot parasites, these will then swim in the tank to infect a new host.
what you need to remember is that the of the shelf white spot remedies will normally only kill the free swimming parasites, and so it is important that you MUST follow the course of the treatments to kill ALL the white spot parasites
hope this helps a bit
im happy to answer any more questions, im not to sure about gill flukes but can find out about them later on for you
