How would I introduce more sand substrate to a tank with crabs?

[Sparroww]

My tank needs more sand it’s approximately at 3-4 in right now. I recently got more playsand and coconut substrate so I was wondering how to introduce it without upsetting the crabs. (It’s 40 gallons with 3 crabs)

[curlysister]

Are your crabs underground? If so, be careful when you add sub that you don't drop it in from a height or pack it down. And don't pull out any decor that are buried in the sand. Some people are extra cautious and only add half to one inch a day.
If your crabs aren't underground, you can add whatever you want wherever you want - you can move the crabs into a container for a few minutes while you add it, or you can just move them over to one side of the tank to add sub then back over to the other side. If you move them into a temporary container, you can then dig and fluff up the remaining sub to mix it with the new.