Today the two butterflies are still doing great! I placed my first order with Tasty Worms to get some Repashy Spawn and Grow to feed these guys so I can promote their proper growth. For now they're doing well on their diet of Soilent Green, Saki-Hikari, and frozen bloodworms.
I decided they had settled in well enough now for me to weigh them and measure their body lengths so I can track their growth over time. I measured length as body length, which means I excluded the tail. Goldfish tail fins are so variable in length that including the tail in the measurement doesn't provide very useful information about the fish. The white fish weighs 35 grams and is 2.25 inches long and the red/white fish weighs 30 grams and is 2.25 inches long. I'm not surprised that although their lengths are the same, the white fish weighs more; because the white one has a more round and full body than the red/white one does.
Since I was already handling them for weight and length measurements, I also took the opportunity to check their vents to determine gender. They're still pretty young, so it's hard to tell for sure, but I think the white one is a female and the red/white one is a male. The white fish has a rounder vent indicating she may be a female, while the red/white fish has a slim and elongated vent indicating he may be a male. I'm very happy that I appear to have gotten one male and one female because I'd like to breed these two fish and raise some butterfly fry in the future!