If he developed anything that is not natural than it is not a good sign. A pinkish color does not sound like a good sign. You're definitely going to want to get some algae wafers from your local pet store and use only one every morning until it gets bigger. Once it gets bigger and can eat more than one you will want to feed it two ever morning. You want algae wafers because they sink to the bottom of the tank immediately and catfish are bottom feeders. What I would do is use more like 75% lake water in the beginning and 25% freshwater. And I would put water conditioner in your water no matter how much is lake water/freshwater. You can find it at your local pet store. There are also other things that could be affecting its health like the pH of the water, alkalinity, ammonia, hardness, chlorine, etc. All of these things can be tested by a test strip sold at your local pet store or they can probably test your water for free if you bring in a sample. I know Petsmart stores will because I work at one. But you will want to check on it soon because your fish may be getting sick.
