In my 90 AGA corner overflow, it seems like the water level is slightly above the top of the overflow slots, so surface skimming does not seem to be happening correctly. Can I just lenthen the slots upwards, or will there be a negative effect? Is there a way to do this while the tank is up and running? Will hall the debris just get sucked into the overflow and caught up in the mechanical media, or is there a trick? Thanks for anybodys help.