I use a 1 gallon ziplock half full with water as a heat sink in my hova. I put that under the wire mesh instead of that rediculous water maze.
The REASON for the water isn't for fluctuation while running so much as when you open the incubator for any reason the air exchange cools the temps(BINGO). The water doesn't drop in temp, thereby giving a more stable temperture
and Edgar, please change that sig, because you are killing my eyes.
i place water in small bowls at the outer corners of the hovabator. In my case it serves 2 purposes.
1) such as what paul just pointed out
2) increase humidity....I live in the desert southwest. Humidity in my apartment is most likely in the range of 10-25% right now and it doesn't go up much outside of winter. I actually run a humidifier during the drier parts of winter so that I avoid getting bloody noses, dry, itchy skin, and sinus infections/bronchitis.