Yes, a tank of warm water the same pH as the discus water.
The reason we agitate or "age" our water is that water under pressure contains CO2. Aigtating or aerating it releases the CO2, stabilizing the pH. This is also why the pH from the tap is generally lower than the pH of the tank water.
Length of time to stabilize the pH varies from place to place. My moderately hard well water (GH 11, pH 7.8) takes about 3 hours of vigorous agitation with a pond pump. It takes more than 48 hours to raise my pH with just an airstone. Other folks with soft ground water from a resevoir may be able to stabilize their pH overnight with just an airstone.
You need a pH kit and to test your water to see how long and what level of agitation it takes at your house. Post your numbers and I can help you guess.