@mangodalat, 100% coir has no fertilizer. And does not hold water. Yes, very difficult.
If your soil is not too hot, it is good. If it is too hot, then some thing without nutrient should be added.
Depend on the strain too. Indica has good appetite and can take rich soil.
I use:
30% old soil.
20% coir, chunky type
10% charred husk (for silica mainly)
10% peat moss
30% Earth worm casting.
I buy directly from worm farm. Very cheap for me.