[cloakerpoked]

As both an aquarium enthusiast, and one who used to work in the retail shipping business, I feel as though I may have something of value to add to this conversation. Our store (an independent) used UPS, FedEX, DHL, and USPS. USPS only guarantees overnight to certain areas, and even then the guarantee is flimsy...I'd never use them. DHL is just a claim waiting to happen, although they'll pay it every time, only had about a 50% success rate with next day or second day service. UPS and FedEx were both really reliable for us...I never really had major issues with either.

As for boxes, as has been stated here earlier...use the smallest possible. Also, use a commercial destination address as often as possible. The rates to commercially zoned addresses are a lot cheaper than to residential, not to mention the drivers ALWAYS know them, they lay on the routes, and get delivered to more reliably. And take advantage of ground if its within the next day delivery zone for your zip. Ground to commercial addresses (with UPS at least) is guaranteed on the scheduled delivery day anyway. Common sense stuff like drop them off close to the pick up time, not at 8 AM on your way to work. All this can help the animals arrive healthy and safe. Remember too...Airplane cargo bays and UPS warehouses are not heated or air conditioned, and the temperature in a brown UPS truck can exceed 110 degrees on a 90 degree day. Even a white FedEx truck will get pretty dang hot on a warm day...don't assume just because the high is 85 that they'll be ok without a cool pack.

Finally, sign up for your own FedEx/UPS account, and print the label and drop it off at a drop off location. UPS stores and FedEx Kinkos mark up their prices significantly from what you would get charged with your own account. You'll also usually have to pay a $5 pickup charge. If you want to make your overnight shipment as cheap as possible...follow these steps:
1.) Use your own account
2.) Make the box as small as reasonably possible, cut it down if necessary.
3.) Ship to a commercial (business) address when possible
4.) Drop off the box as a drop off location