normal for humidity gauge to fluctuate a lot?

[fantasybookworm]

I have a digital thermometer/hygrometer that I bought from a pet store (I can't recall the brand...I think Zilla?) several years ago. The temperature has always been accurate (I used to use it for my hedgehog's cage), but I'm wondering about the humidity part.

I tried calibrating it last night to tell how much it's off by. It was reading 7% under when I checked, and since it's digital, I can't change that, so I just wrote it on tape to put on it so I don't forget.

I'm just not sure if it's normal for humidity to fluctuate a lot or if maybe that might be broken & I should get a new one? It's gone from about 45% up to 54% since I got home. The only thing I've done is add more water to the salt water pool, which didn't seem like it'd have that large of an effect! Any comments on whether it might be broken or untrustworthy?

(And yeah, I know the humidity is way too low. I got some supplies today so I can try to hook up my warm-air humidifier so the air goes directly into the tank to help get that humidity up to the proper levels!)

[CallaLily]

Adding water may have given the humidity a little boost. What sort of lid do you have? You may have already seen it, but just in case, this thread has some tips for creating and keeping humidity.

[fantasybookworm]

Thank you! I've been reading over that for more ideas. I'm going to see how the humidifier changes it once I get it cleaned (with vinegar). I have a screen lid, so that's going to make things difficult. I may get some cardboard to tape over part of it to help maintain humidity. I think I'm still going to hook up the humidifier though, because my house tends to be on the dry side, especially in the winter with the heat going.

[wodesorel]

Cardboard will wick away moisture. Try plastic wrap, or plastic packing tape.

[fantasybookworm]

Okay, thanks! I used craft foamboard from Michael's instead of cardboard, but it still seems like it could have that issue. I think I'll take it off & cover the tank-facing side with packing tape tonight, to be safe.

[Sassypants]

I used two layers of Glad Press and Seal wrap on top of the screen in my 10 gallon iso. It's lightly sticky, so it stays on the screen just fine, but doesn't endanger a climbing crab. It does a great job keeping the humidity in, and is also translucent, so light can get in. I used a dome lamp with a CFL bulb right on top and it worked great. The CFL bulb is not hot, but slightly warm. It would bump the temp up a degree or two when it was on. I cut two of the corners of the wrap at an angle so there was a little air flow. The set up stayed consistently at about 82*, and 85% humidity.

[Asheka]

I have sheets of coroplast ( http://www.homedepot.ca/product/white-c ... nch/924854 ) I had planned on using as a temp lid while the plexiglass one I've designed is being cut. You can get them very cheap from hardware stores in all sorts of sizes. I had bought 10 of them to make a playpen from when I had rats. They'd need to be weighted down to keep escapees from pushing it off as it's very light, but wouldn't wick moisture.

[fantasybookworm]

Coroplast is great, I've used that for a homemade cage for a hedgehog.

I think I'm going to use packing tape taped on the inside of the lid so light can still get through (though it means they won't be able to spidercrawl, but they don't show much inclination to climb yet anyway). I'm also picking up a different style of humidifier after work today. I don't have time to make a homemade one right now (I chose the worst time to bring these guys home, really), and I really need to get the humidity fixed. I need to fiddle with the lamps again, as 1 lamp + 1 UTH (for a 40gal tank) isn't keeping the tank as warm as I'd like (around 76-79*).