If you’ve got an aquarium that’s been sitting in storage for a long period of time, be sure to inspect the silicone seams between the glass before you even think about filling it back up. The silicone can dry rot even in a short amount of time, causing them to shrivel and crack. When this happens the tank may still hold water, but the chances of it failing are significantly increased. And that failure won’t happen when you’re at home, or even in the middle of the day. Chances are it will fail while you’re at work, on vacation, or sometime in the middle of the night when you can’t get to it to fix. To prevent this, you can keep the aquarium full of water, even if it’s not running, or you can put some sort of moisturizing liquid, such as a petroleum based lubricant. Again, the idea is just to keep those seams from failing.