When I buy new tanks I put them on a clean dry towel... fill them to the top being very careful not to spill any water on the towel... wait a few hours (overnight usually)... then inspect the seams, carefully drain the tank and review the towel for wet spots...
If it doesn't leak overnight then the tank doesn't leak... if the seams are weak and might give way, then it might take a day, a week, a month or a year for this to happen. At some point you have to decide it's strong enough to try in the house.
Pay close attention to the condition of the silicone before and after you fill it. If there is even the slightest change then monitor it longer or don't use it inside. But if there are no changes in the silicone after sitting full overnight, I'd trust them.