Koi tattoo

Hi I was wondering if anyone could tell me why some koi fish tattoo's appear with forehead rings. I've seen some Koi tattoos with no forehead rings and some with upto 3 forehead rings and wanted to know if they have any significant meaning. many thanks mike

The reason i ask is because i'm starting my 1/2 sleeve this weekend and all but this aspect of the design have been finalised, i don't want to leave the forehead rings out if they have some sort of meaning. Any info you may have would be greatly appreciated! (btw. i have checked all the Koi related posts on this site) I have tried all over the the internet but cannot find any info! i thought i'd ask you guy's seeing as some you are tattooists and seem fairly knowledgable. Cheers mike