No

No. Hermit crabs should not be under heat bulbs, it will cook them and kill the humidity. Plus, hermits should be in sealed tanks with an acrylic or glass top lid since they breathe humidity, so having a heat source above glass could cause a break. Instead, you need a heat mat along the entire back wall, above the 6 inches of substrate they need. Hermit crabs are a lot more work to do properly and will live longer if you do outside research. It's also 10g per hermit crab, and they're social so there should be a minimum of 2; so a 20g long is really the minimum for 2. Plus you'll need 5 natural shells per crab... so you're looking at a decent amount of space with a heavy tank since you need 6 inches of substrate with a 5:1 ratio of playsand and eco earth. It's important you don't use Hermit crab specific sand since it's all Calcium sand, which will collapse their tunnels and kill them. It's look at Crab Central's YouTube channel for info on them because they're amazing pets, but really do require a fair bit of outside research.

I cannot tell you exactly how much heat the Nano basking bulb will provide as it depends on the temperature of your house and the size of your enclosure. You can try the 25 watt Nano bulb and see if that is still getting to hot, if it is you can always try adjusting your lamp a little higher up to decrease the heat.

The Nano basking spot lamp does not provide UVB, you will need another bulb like our Reptisun 10.0 or Reptisun 5.0 bulb for UVB.