I already have gravel and water in my tank (no fish-not cycled yet)
can i add some sand to go in a bare spot in the gravel while theres water in the tank
Can't see why not, just make sure you turn off any filter whilst you add the sand, and then turn it back on as soon as the sand has settled on the bottom, you dont want any going in the filter intake!
I use a mixture of sand, gravel, laterite and fired clay in my tanks, and my plants love it! My digging crew enjoy it too