I beg to differ. I think you absolutley need them. If you dont have proper humidity then you get bad sheds and then there are also times when your tank is tooo moist and you cause mold to grow.
If it's wet enough to grow mold, you can see that it's too humid - the enclosure doesn't dry out, the branches and leaves are constantly damp and a slime coating starts to form. Most likely when you open the door/lid, you can feel the moist stagnant heavy air rise up at you. If you're observant enough, you can tell when things are getting a bit too wet, dry or just right, no need to check a gauge. Normal room humidity, along with a light morning misting and a heavier one in the evening has worked well for me and my Rhacs since 1997, no gauges needed. Even in winter with the furnace drying things out, they still don't have bad sheds and I have no clue how humid it is in the enclosures.
Also if temps get to high, the gecko could die and as well as too cold.
Rhacs are comfortable in the same temperature range as you. Too hot for a Rhac means you'll be uncomfortable as well. I don't have A/C, we get whatever temperature summer throws at us. I only know how hot it gets for my Rhacs because of the weather reports. A thermometer will tell you the same thing, but it won't help cool them down.
They've been observed active and hunting food in the wild in the high 50F range. If your temperature is cold enough to kill a crestie, then you should be turning on the heat for your own health as well.
I put mine in the bottom of the tank as it has a foot on it with no velcro needed...
Putting a hygrometer on the substrate isn't going to give you an accurate idea of how humid it is where the geckos are, unless they're sleeping on the floor. It's going to be less humid higher up where the geckos are. Ideally, you'd have to measure the humidity at various heights so you know if they're sleeping the day away in drier areas or super wet places. Same with temperature - you can have a temperature gradient throughout the enclosure. Measuring one spot won't tell you the maximum and minimum.
If you do want to get a thermometer and hygrometer, then at least get a good quality model, cheapies are known to be completely off. The small round stick-on ones are notorius for wrong readings. The needle can stick in a few months, sometimes even weeks.
Hygrometers and thermometers are a 'must' item for some species, particularly the fragile ones. For Rhacs, just go with common sense, save the money for more geckos.
