more stable? that's debateable, you cant assume just because you have more water that is of better quality, although parameters might change more easily in smaller quantities it does not mean the water is cleaner i.e filtration and water management obviously play a vital role.
i know aro's are top dwellers, but if there was less water would it not be easier for the fish to find food.....in the example of blackworms that sit on the bottom if the water level was dropped 20cm would it not be easier to swim to the bottom to pick up food.
yes i know they are surface feeders as well....i've seen aro's eat off the bottom, by leaving blackworms at the bottom they will not pollute the water (ibviously with sufficient filtration) and he could eat anytime, if he wanted to. i would find that easier than constantly having to drop food in the water, seeing if he is eating, and then having to fish it out.
just my 2c and personal opinion.