Hi, I am new to this, but from what I have learned a white spot is an indication of bacteria, now first of all, he is not going to die from this. You must figure out what is going on in your tank. Now the condition of the water is important, as well as the basking area, as they all must dry off every day, so good UV light to provide warmth, up 80's, thermometer to check temps, UVB light will help with the calcium and vit D absorption,I use a 10.0 bulb, ok I also have a good filter, and I have an ammonia wheel in the tank, sits in the water, sticks onto glass..I do weekly water checks, ph, nitrites, nitrates, I have kits for these, and I do partial water changes, I have some live plant and I sprinkle calcium from cuddle bone, as well as I leave a small chunk in water...the temp of the water is 78-80, and I keep things consistent. I have a growing healthy Map Turtle in a 20 gallon, soon to be moved to a bigger tank in near future. I think personally when you know everything is running smoothly, the white fungas will disappear. You could also add a sulphur block in the water...start by doing some water checks and lighting, a pet store will do the water check for you...go from there and this should help clear it up quickly....hope this was helpful, Susan...