Do the 'swords' on swordtails change colour?

[the_elvish_misfit]

I have a male and female Swordtail, they're both completely solid orange. I noticed today that the bottom of the male's has a perfect black line all along the 'sword' part from the tip to the base of his tail. It wasn't there before, I even went through the thousands of pictures I've taken and his tail was orange. Does this normally happen?

 

[the_elvish_misfit]

Actually now that I notice it, he occasionally swims erratically on his side, even slamming into the ground. Should probably ask solutions to that too.

 

[bloodylankan]

my swordtail has a solid black line too...buh its been there ever since I had it...just actually swims weird at times too...swims around circles around and goes up and down like hes going crazy or something..

 

[MichaelsLilGray]

As long as he isnt scraping the ground when he does it.. (which would be a sign of ich...) sounds like a normal sword to me.. just keep in mind.. they have a box they live in.. they get bored lol