Yeah, denisonii was what I was referring to. I just worry about finding them at a decent size so the ATF doesn't immediately go after them as food.
You're not kidding about them being more expensive than a normal dither, I saw some huge roselines 5-6" and thick at an LFS nearby and they wanted something like $50-$60 apiece. I've seen smaller ones at Petsmart for $9 apiece (which would absolutely be quarantined by me if it happened), but they're in the 2.5" - 3" range. I doubt very seriously that my GATF would leave them alone at that size.