If you purchased an aquarium that has not shipped yet, then you can call and add a Waterbox Care plan to that aquarium. Be sure to have the original order number for customer service to get the correct plan on there.
If you are the original owner, you can add a Waterbox Care Extended Manufacturer Warranty as long as the original manufacturer’s warranty is still valid.  If you purchased from a Certified Retail Partner you can still extend your warranty, as long as you have proof of purchase.