I currently have two crayfish in a very small tank and I'm planning on buying a 24"x8"x9" fish tank for them (I guess height doesn't matter?).

I'm planning to buy some caves and plenty of small to medium size driftwood (I'm young and poor). Also planning to use gravel (is it better than sand?) and I have a small air pump (Is one enough?) and a manual filter pump (again, I'm poor). The air pump is quite noisy, is it ok to turn it off during night time?

Additional Notes: They both have molded around 3 months ago, they are both 3.5 inches long (tail to claw), red colored with orange dots, I don't know their gender. I have an elodea (water weed) farm set up, their main diet is dried shrimps, cabbages and water weed (maybe some small fish specialized for feeding).