Ego Anglice dico.
After some research, I have determined that the correct Latina translation for "Armedblowfish" is "Armata Diodontida". Armata is the feminine perfect passive participle of armo armare armavi armatus. Diodontidae is the scientific name for the family of porcupinefish, which is the type of blowfish I am referring to. Scientific names are Latina, and the singular of Diodontidae is Diodontida. Diodontida is feminine, hence the feminine participle armata is used. It would probably be conventional to put the participle after the noun, but since word order is flexible, I lined it up with the English version.