Calligraphy inks come in a wide assortment of ink ‘types’.
There is the traditional ‘India’ ink, specialty calligraphy ink lines, fountain pen inks, watercolours, walnut ink, gall ink and Japanese ink sticks or ink cakes.
Some are lightfast, some are waterfast, some are archival.
It is important to know your ink so you use the proper pen type for your Calligraphy work. Inks that are created specifically for Calligraphy should not be used in fountain pens. Fountain pen ink, however, can be used with either fountain pens or Calligraphy nibs. Watercolors should be used only with Calligraphy nibs. Gall ink can be used both ways, however, if you use this ink in a fountain pen you have to maintain a careful cleaning regimen so as to ensure the nib does not corrode.
Many inks and many ways to use them! Try different ink types to see what works best for your writing style.