I have Walnut in an Edison Collier and Dark Matter in an Eco at the moment. Walnut is "bulletproof."

Noodler's Ink Dark Matter is not. It is, however, a recreation of the official ink of the Manhattan Project. The ink wizard behind Noodler's was sent a bottle of the original Manhattan Project ink, and he chemically analyzed it, and reproduced it as closely as he could manage with modern components. Scientists and clerks were required to us it so any materials could be traced back to the project. The bottle has a picture of Oppenheimer on it.

Bottles of 54th Massachusetts and Heart of Darkness lurk in my closet waiting to come round in the rotation.

Avoid Baystate Blue!

Counterpoint: BSB is my favorite ink

Why?

It has a reputation of staining everything and notoriously difficult to clean out of some pens.

Baystate Blue also seems to be a cursed ink. It's not a matter of if you drop that bottle, but a matter of when.

It's a vibrant blue and is an archival ink. Cannot remove it and it's impossible to miss when you stain something with it. It'll stain your fingers for days.

If you drop it on a rug, or countertop or spill some while filling or cleaning a pen it's a major pain to clean up, if you can even clean it up.

It also has a reputation for staining the ink reservoir of your pen and if you have a fancy demonstrator to show off the ink you'll only ever see blue and none of the fun colors you're using.

Which is why Noodler's Ink issues a free fountain pen (The Charlie) with the 4.5 oz. eyedropper bottle. You can use that, or you dedicate an inexpensive pen, like a TWSBI Eco or a Pilot Metropolitan to the ink. (Many do this.)