HCA: Hermit Crab Association

Whether or not you need heat pads will depend on how warm the new overhead heating will keep the tank. Before buying something you may want to set up the new tank - moist substrate and heating only - then see what temperature you have as a starting point. Since you already have the crabs in a reasonable tank you have the luxury to set up the new tank slowly. Getting a new tank set up and allowing the conditions to stabilize is helpful. If you have a 75 gallon and a large crab I'd recommend 6" to 8" of substrate (more is better). That takes some time to heat up. Also, I've noticed that the more damp substrate you have the better the humidity will stay up.

If you do need a UTH I highly recommend the Ultratherms. They are only available online, but have several advantages over the stick on kind. For one, they tend to provide more heat. You can also insulate behind them with polystyrene (blue board from the hardware store) and can use a dimmer with them to turn them back when you don't need as much heat. They are available at beanfarm.com and retilebasics.com.

I was just wondering if the overhead heater would dry out the tank. I haven't put it all together yet but my mom mentioned that to me and I have a lot trouble keeping my tank humid.

Anything you do to raise temperature will by definition cause the reading of relative humidity to fall; it is a matter of balancing the two factors back and forth until you get both the temperature and humidity within good ranges. I'm heating my 55 with only overhead lighting, shining through plexiglas lids that my husband made for me. It's plenty warm, and so far, it is actually too humid (often running in the high 90's in humidity). Needless to say, I have not put crabs in there yet. I'm hoping small in-tank fans will be the final solution to balancing everything. Humidity is provided by: 1) deep substrate initially moistened with 1/2 strength marine salt water and kept at "sand castle" consistency; 2) moving water: bubblers in the salt water pool and a fountain for the fresh water, and 3) live plants.

Personally, I like to use a combination of UTH and heat light. That lets me keep both at lower heat levels. I like having the overhead heat since that is what they would experience in the wild from the sun. I also don't want that to be super hot because it does tend to dry out the surface. Like I said, that's just my preference. There are people who successfully use just a UTH and who successfully use just heat lamps. I think some of it is experimenting to see what works best for you.

Can the overhead heating be put on a dimmer? Is it a lamp or something else? You can get a lamp dimmer at the hardware store for about $10 so that may be an option if it creates too much heat.

I'm setting up a 90 gallon now and will be using a 48x11 Ultratherm on the top back and and large zoomed UTH on the one side. The large back Ultratherm will be on a dimmer, this way I'll be able to have one side a bit warmer then the other.

I use lights now and the issue I have it I can't see inside the tank as well as I'd like, so this time I'll use florescent strip lights.