I have had this 10 gal tank for a few months now and I have two guppies in it. One has an orange tail with small white and red dots in it and I have done research and believe it is fungus. My other guppy has been recently tail pinching and has very minor finrot. I have tried using tap and distilled water and salt. I just recently added two plants and I also have an undergravel filter. I do water changes every sunday and their tail fungus seems to be slowly clearing up but they still dont seem active. I also just today added Prime water conditioner. Is there anything else I could do to help them? Water levels are: GH 30 KH240 pH~7.5 Nitrate 20 Nitrite 0.5 slowly decreasing. Any advice would be greatly appreciated. Is there a possibility of parasites or diseases??