Don't raise it over a week. You need to get the temperature up to 30C (86F) asap and keep it there for 2 weeks, or at least 1 week after all the white spots have gone.
If you have the fish in cool water (less than 24C), then raise it up over 2 days.
If the water is 24C, raise it up to 30C over 24 hours.
If the temperature is 26C or above, just turn the heater up to 30C and let it go up.
Before you raise the temperature, do a 80-90% water change and complete gravel clean. Clean the filter too. This will remove a lot of the parasites and leave fewer behind to reinfect the fish.
If you are raising the temperature over 2 days, do a big water change and gravel clean each day until the temp is 30C.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
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The following link has information about white spot and various ways to treat it. Post #1 and post #16 are worth a read.
This is a common question that is often asked, what is ich and how is it recognisable and what causes it? The real term is ICHTHYOPHTHIRIASIS. OR commonly known as white spot. It is an extremely comon parasite that affects aquarium fish. It is highly infectious and potentially lethal and...
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