What kind of ink is good for writing hard pen calligraphy? !

I have been using ostrich brand since primary school. Very good, the color is very positive, there are pure blue, blue black, black. It does not block the pen at all and writes smoothly. It is the best pen water I have ever used, and the price is very cheap. Later, I used some expensive ones and thought they were not as good as ostrich cards. I hope it helps you ~