Well, for one, these are certainly very different creatures than the LEGO line of Bionicle toys. xD
On one hand, it wouldn't matter quite as much unless you were making money off of this species-- which you aren't (I don't think).
On the other hand, if you're still concerned, you could do one of two things:
1.) Change the species name-- just the tail itself is nothing to worry about. Or
2.) Simply post in the species thread, "These guys were inspired by Bionicle," perhaps also giving a link to the Bionicle site, that way you're still giving the nod to the creatures that inspired them.