im guessing you are getting ich from low water quality. or stress on the fish, water changes should be caryed out with room temp water, you acheive this by making the water 24 hours before adding it, then removing the "old" water and replacing it, just toping up for evaporated water wont cut it because toxic metals in your water will build up (they dont evaporate) and can cause death.
weekly water changes are essentual, i'de say twice weekly both 10% so you do a 20% water change weekly.
try making life less stressful, when adding: on the journey your LFS should rap the bag o fish in a brown paper bag, this reduces the stress for the fish and helps keep the heat in, keep them in the quiet and warm. when adding them, float the bag in the tank for 20mins to equilise the temp then every 5(ish) mins add some tank water into the bag (open toped but still floating) so your fish can get used to your water. do this for 45mins then net them out the bag and into the tank, dont take them out of the water for more than 1 second because this will cause emence stress (the time in air wont kill them as fish can last 5-10 mins out of water). through away the water in the bag and keep the tank light off and in the dark for 2hours minimum (i usualy do it for 6+, by which time its bed time). dont feed them for a day or so, then start feeding once a-day with a small pinch of food.
diet (the high lighted are not nesasary, it will say what they are for)
diet should be varied to keep you fish in good condition.
- the main foods it should comprise of are:
- live bloodworms every few weeks - months (optional, but recomended)
- frozen bloodworms once a week
- live brine shrimp every few weeks - months
- most live foods
- a pea or two every 2-4 weeks
- flake food for top feeders
- micro pelets for mid feeding fish
- fast sinking tablets for bottom feeders such as corys and catfish
- algae wafers for algae eating fish and snailes
keeping water quality should be a key, and keep filter maitinence up, a cloged filter wont work at full pase. find the cause of the problem and work on from there.
hope this helps, shang hi
PS. i wasn't saying you dont do water changes or dont feed your fish well, its just some help.
EDIT: forgot some food types