There are two improvements that can be performed on potion of poison (and generally on most potions):
- Redstone dust improvement - makes potion last longer
- Glowstone dust improvement - makes the potion effect stronger while decreasing the effect strength
Since the Potion of Poison deals damage over time, it's a question, whether more damage will be dealt with increased duration or with lower duration but higher DPS.
Does anyone know the answer?