I was tired of seeing air tubes all over the tank and didn't like to suction cups with clips. Note this tip will require some silicon work and you will have to empty the tank.
1. Empty your tank and dry
2. Go down to your hardware store and purchase some 6mm clear piping. The local hardware store was selling the 6mm piping in small section and as joiners for larger tubing. I found these in the gardening section
3. Silicon the 6mm piping to the corner of your tank and allow to set
To my knowledge, the air tubing is 3 or 4mm so it has no problems sliding thru the 6mm tubing. To clean the inside of the 6mm tube you can just use a standard tube brush. You could opt for a single length all the way down inside of the corner but i believe this will be a hassle to clean.