Hi MatsP,
Pretty sure they're K. minor, I checked the spine before I bought them and it is clear with darker shading on either side, the spine itself is not black or dark at all. I looked at the other Kryptopterus and it doesn't look like any of the others either. Very nice match with the pictures of K. Minor. One of them is close to 2 inches though so they're kind of large compared with the little cardinals.
They've been swimming in all areas of the tank during the day and hang together in a group in the evening. They get kind of wild when I feed them so I was thinking maybe the feeding frenzy was scaring off the smaller cardinals and causing them to look for "worms".
They were at the store for over a week so they look nice and healthy, no spots or anything. Very pretty fish. I'll be adding to the shoal if all goes well.
Racing, shoes and fish. Nothing else matters. Oh, and bacon.