yup. thats really the only way to do it. Is it a used tank? if so i would inspect all the silicone seals even before adding the water. If it is dry/flaky, peeling away from the glass or damaged i would fix that first and then try the leak test. Good Luck and keep us posted.
If im only suspecting the tank to leak on the corners at the bottom can i just fill it up say a couple inches and wait and see? or do i have to fill it up to the top?
I would fill it all the way. THe drips are always spotted at the bottom corners but the leak is often part way up the corner. If you fill with a garden hose it wont take too long to fill.