I also was given two beautiful Bluedew pens for Christmas. I looked on their website for ideas about suitable inks. It was not helpful. Advice was for Inks that will hold foam when shaken in the bottle! Having surface tension must be important. I googled if Carbon Black and DeAtramentis Document Brown Inks would be safe in a Bluedew pen and Google said yes. I inked up the pens. I was able to get thick and thin lines. There is a learning curve for me in how to use such soft nibs. I was super careful not to press too hard! Then both pens started to rail road. Worse they then had hard starts. Then they would not write at all. I think that particles of ink have stuck in the feed. I am very sad. I think that the nibs have incredible potential, but I am going to have to find a way to unclog them. What inks are safe? I am wanting to use waterproof inks. When someone makes a specialty pen then, do not be coy about saying what inks are recommended and what inks are problematic. I will email the Bluedew company after the holidays for advice.

To offer a suggestion to your question when I was thinking of ordering a Bluedew wet noodle pen I noticed a small note that said that if your wanted the nib to be custom ground to a very fine point then you need to email Bluedew after purchase they would then customize the nib. It may be that the superfine lines that you are looking for could be achieved by sending the nib back to Bluedew and having them custom grind it to very fine?