I have an old galvanized metal Brower brand incubator and 5 styrofoams and one really old metal one with no brand name on it but I use it when I need to. First of all I will take my metal one over the styrofoam one any day. I check my incubators constantly throughout the day because I have found that they are very unpredictable when it comes to temperature. Humidity is usually what ruins a good hatch. In my metal incubator I might put a tablespoon of water in it at night or maybe less. I usually base the amount of water I use according to the humidity in the room. I do not use those cheap thermometers that come with the incubators, those things are worthless. I have invested in several themometers with the probe that I can put down through one of the holes in the top of the bator and tape it in place. I put the probe down till it is at the top of the egg. The foam bators have a tendancy to start letting the water seep out of the bottom of them after a couple of uses so I have found two fixes for this. One is to line the resovoir with aluminum foil or set little dessert cups under the wire, being careful not to cover the vent holes in the bottom. Of course you have to cut the cups down till they will set under the wire. The foam incubators will form more humidity in them then my metal one so I have learned to go by feel. When I open that foam bator to turn my eggs and I can feel the moisture in there then I don't add water at all. Those last 3 days is when they really need the most humidity so that they don't dry out while trying to hatch. I haven't hatched any chicks for about 4 years now but I now have 77 eggs of various breeds, some barnyard selections and a few bantys to hatch on April 25th. I am expecting a decent hatch if nothing goes wrong such as a bator malfunction or loss of power for an extended period of time.