In the long 20 gal tank I keep at my parents' house, I have a Black Moor and a Fancy Goldfish(*) (plus 4 small comets). Both are about a year old, and are pretty happy and healthy for the most part. However, when I last went home, Cody (the gold), was making what seemed to be, I kid you not, a bubble nest!
He was actively chewing and spitting out bubbles, and had made a layer around the right side of the tank (furthest away from the filter) about 2 inches deep at the thickest.
He seemed happy and healthy, with really great color and full, flowing fins, while Zach, my moor, was swimming around normally, with no special interest in his best bro.
I'm just really curious, what the heck is he up to? I haven't bothered with trying to sex either of my babies, could this be a sign of maturity?
*actually, looking around at types to make sure I'm identifying my gold right, he might be a Telescope Goldfish, since when I bought Zach and Cody, they were no more than 2 inches long and I thought they were both Black Moors! Cody only just recently finished turning gold from his original black.