At the end of the day medicated water retains its original color which I assume means less degradation from UV rays. Because it's round birds seem a bit confused and circle the entire thing looking for the opening but if you put the opening right up against a wall the wall guides their head right to the opening.
2.5 L is great for medications because 2 liters is an easy amount to mix up with most dosages (1/2 teaspoon when it's 5g medicine per gallon) and on a hot day 2 liters seems to suffice for about 20-30 birds.
