Another tip that you really must do for a successful refill of your canon BCI-3 cyan, magenta,  yellow , black or any photo ink tank is to hold the tank at a 45º angle as you are injecting the ink, again keeping the ink from entering the sponge area as you are injecting it.  Let the tank sit on a 45 degree angle for about 30 minutes after refilling.  Return the tank back to the print head, install in the printer, and run a cleaning cycle as described in your users manual.
 

If the canon BCI-3 cyan, magenta,  yellow, black or any photo tank is printing somewhat but not quite 100%, click on one of our TEST PRINT pages.  Repeat printing this page till you get the perfect copy.  Normally, doing this will work out any air bubbles that may have gotten trapped in the sponge as you were refilling.  Once the air is out of the sponge the tank will release ink instead of air, resulting in a better print.