Glass 20 gallon tank - should it be fully covered?

[Zolthux]

We recently got a hermit crab for my son and we spent the better part of the weekend getting it set up.

We bought a 20 gallon glass tank, heating pad (attached to the side), mixed and added substrate(mixture of the brick and sand), put sensors for temp and humidity, etc etc.

The only thing we are unsure of right now is the lid: we bought a glass lid from petco, but I think it'd too small. Even adding the plastic/vinyl extension, there's a clear gap along the long side of the tank.

Are the lids supposed to be airtight? If not, how much space should thr opening be? Is it okay if it's got a few cm along the long end of open space? I thought it had to be fully sealed to maintain the heat and humidity inside constant

Thanks in advance!

[JoeHermits]

Usually you want at least the entire top covered so crabs can’t escape. If the gap is too big you may have to either get a custom lid (glass or plexiglass) or use a screen lid (which you can cover with plastic wrap to hold in the heat and humidity better)


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[Zolthux]

Thank you for replying! I am not concerned with him escaping ATM, my primary concern is that he has good living conditions. Curre try he's spending his time under the substrate (coming out at night), and his tank is foggy.

Will sealing the tank help with the fog? Is fog okay?

[curlysister]

By fog, do you mean condensation on the inside of the glass? If so, that's because of temp difference between the tank and the room. What are your temp and humidity readings?

[Zolthux]

By fog, do you mean condensation on the inside of the glass? If so, that's because of temp difference between the tank and the room. What are your temp and humidity readings?

We had the tank outside in our screened back porch. We moved the tank inside the house.

We are going to try buying a larger heating pad because the indoor tat temp is like in the low 70s

[curlysister]

What is the humidity in the tank? If it is low, you will want to cover more of the lid to hold the humidity in.
You can also insulate the tank - some brands of heat pads can be insulated over top, but others can not so you would only insulate the sides and back where there is no heat pad. Folding up a blanket on the top of the tank also helps hold in a bit of heat.

[Zolthux]

I just checked the tank the morning and he's at 73F 75% Humidity

I ended up getting a second of those glass covers and using it to cover the rest of the gap. I'm gonna look into getting a custom cut glass top so I can seal the whole tank though.

As for using a blanket to insulate. I'll try that!

[Zolthux]

Quick update: the conditions have stayed steady, and after almost a week, the Lil guy has come out of his burrow