Company will not honor a three-year warranty

In July 2009, I purchased an aquarium filtration system manufactured by this company. The purchase was made through the vendor eBay.com. I have proof of purchase and shipment. In July 2010, the filtration system sprang a leak. The filtration system has not been in use since. I contacted Eheim back in July regarding this issue, but did not receive a response until recently. Eheim claims under their company policy, the warranty is voided because the item was not purchased through an authorized Eheim retailer, to wit: eBay.com. My position is their warranty does not implicity or explicitly state that the filter had to be purchased from "an authorized Eheim retailer" as it merely states that the item must be accompanied by proof of purchase and delivery to be covered under the 3-year warranty. After exchanging over 9 emails back and forth arguing our respective positions on the issue, Eheim remains stubbornly firm on their stance, and refuses to offer a compromise or resolution. Further, Eheim no longer responds to my emails. Eheim needs to act in a diligent manner, take full responsibililty of their defective product, and make the necessary repairs to my filtration system as promised in their warranty.