Canon lists and sells ink cartridges compatible with the Pixma MG2520 printer at Canon.com. The correct cartridges are the PG-245 for black ink and the CL-246 for color ink, including the XL version of both cartridges.
From Canon USA's main website, type "Pixma MG2520" into the Search Box. Click on Supplies and Accessories under the product result. Purchase ink by clicking to select either individual cartridges or one of Canon's combination offers. Then click on the Add to Cart icon, and continue with the checkout process.
Canon's PG-245 and CL-246 cartridges use Full Photolithographic Inkjet Nozzle Engineering, or FINE, technology. Cartridges with FINE create smaller droplets than ordinary cartridges and expel the ink faster, meaning images are printed with high detail and precision. Furthermore, FINE increases a cartridge's efficiency by expelling all of the ink directly under the heating area at once.
The XL type of both the PG-245 and CL-246 has a higher ink capacity than the standard version. An XL size cartridge will print more images and text than the regular size. It is also possible to combine cartridge sizes. For instance, someone printing black and white text documents and few color images could use a PG-245XL with only a standard CL-246.