How to Measure for Custom Cutouts

All measurements for your cutouts must be taken from the outside (external) face of the glass, not from the inside of the tank. The lid sits on top of the glass rim — so your cutout dimensions need to match what the lid will see from above, not what you see looking down into the tank.

Hook your tape measure on the outer edge of the glass — this is your zero point for all measurements.

The width is how wide the opening runs along the edge of your tank — left to right across the side or back wall where the cutout will be. Measure the full width of whatever needs to pass through (light mount, cord, fitting, etc.) at its widest point.

Measure the width of the cutout opening along the tank edge, then add ⅛" for clearance.

The depth is how far the cutout extends inward from the edge of the lid — front to back across the rim. This is how much of the lid gets cut away so your light mount, cord, or fitting can exit. Measure from the outer edge of the glass to the back of whatever needs to pass through.

Measure the depth from the outer edge inward to the back of your fitting, then add ⅛" for clearance.