Red veins visible on oto's belly? Or bizarre disease/injury?

[LeahK]

There are weird red lines visible on my oto's belly. The lines make a little diamond shape right between its pelvic fins. There is also some red where his pectoral fins meet his body. I first noticed this tonight.
My numbers are good: 0 ammonia, 0 nitrite, 15ish nitrate. The fish is otherwise active and eating well. My husband managed to catch a few good shots. He says maybe it's just the fish's veins showing through its skin. I'm more paranoid. :) Any ideas on what this is?

http://i251.photobucket.com/albums/gg313/LeahKa/IMG_1004.jpg

http://i251.photobucket.com/albums/gg313/LeahKa/IMG_1005.jpg

http://i251.photobucket.com/albums/gg313/LeahKa/IMG_1006.jpg

[fishorama]

Red streaks are often a sign of bacterial infection. How long have you had him?

[LeahK]

I've had him for about 2 months now. He was in QT for about 3 weeks, and then went in the main tank. I googled septicemia, but I'm not sure if this fits the description.