Ditto on the above remarks. The 350 ml of Pilot blue-black is what I use for teaching, along with the red. You cannot top the price, and it is a quality ink.
You've being really limiting yourself with Pelikan 4001 and Bril Blue, just as you have by focussing on a Pilot Metro. Get another pen (Moonman makes some lovely, very inexpensive pens that top Pilot Metros, as do TWIBI Ecos) and a couple of inks. You can a little freshly-boiled and then cooled (about 10% by volume) distilled water to safely extend highly-saturated inks such as Noodler's.
Diamine inks are, pretty much across the board, good inks and good buys as well, and you can often find them in 30 or 80 ml bottles. They've been around since the mid-19th Century for good reason. You could buy only Diamine the rest of your life, and miss almost nothing (see below).
Waterman inks have long been worldwide standards due to their fine qualities and fair price. I am so very fond of their lack of pretentiousness. They get the job done and deliver true value. I personally use their brown a lot where others use many brands and shades of blue or blue-black. It is addictive, attractive yet serious enough, and easy on the eyes.
My friend, I do think you are missing something if you don't eventually try either Black Swan in English Roses or Black Swan in Austalian Roses, by Noodler's. They leave me breathless. Almost in tears. I bought the second when all I had was a Pilot Metro to use when my old, long-beloved Parker broke. I prefer them in that order given, and they are simply knockouts; they are cheap, too, given that you get 3+ oz of ink. Lovely, lovely inks to write with, and simply lovely to behold, and I am a determined Noodler's skeptic as six years later, I still only own five of his inks, two for their bulletproofness; on that particular day of creation, however, genius, high art, and perhaps even God, were hard at work together. They will not allow me to be stinting in my praise. Save up, and then savor. You only need a bottle of one of them. If you were nearer, I'd give you half a bottle of one of mine.
The Swans vary a bit lot-by-lot, but never swim far away from their sheer beauty. Let them swim into your life and make you smile.
Edited by Brianm_14, 01 September 2019 - 20:55.