Well, I thought I'd give an update. I have not seen Sparkie bite his tail in the last day or so, and the catfish are getting a little braver. Sparkie will still occasionally chase them, but other times he swims right by without paying them much attention. When he does chase, they skitter off and hide in the plants for a little while, and then slowly make their way out again. Also, Sparkie has made big bubble nests in the last two days.
So, I think they're getting used to each other. The only thing I'm still concerned about is the tail biting. He hasn't done it lately, but he bit it so short on that first day that it doesn't fly in his face when he does a quick turn anymore. So, I think it will start growing back now. But once it grows back to that level, will he bite it again? I guess I won't know that for several weeks, but I would like to decide by this weekend whether to keep the catfish.
Well, I will see how I feel about things by the weekend. If I do want to take the catfish out, I think I might have to completely rip apart the tank to do it (remove plants, etc) because they are SO fast and good at hiding!