Whether you have commissioned the manufacture of your frag tank or you are going the DIY route, at some stage you will need to determine where you would like the inlet and outlet holes drilled.
Your choice will be either drill the side of the tank or drill the bottom of the tank.
DRILLING THE SIDE OF A FRAG TANK
This takes a little more thought than drilling the bottom in that you will need to plan the exact height of the return and drain.
The inlet should be no less than 60mm at its centre from the rim of the frag tank. This will ensure that a third of the drain will be proud of the water surface, and that there should be 40mm between the water surface and the rim of the tank.
The outlet will be placed no less than 50mm at its centre from the rim of the tank.
The top of the return will fall just below the surface of the water.
Therefore, the outlet will be just below the inlet.
If you plan on using an emergency overflow, this can be drilled low on the side. Use an elbow to extend the drain to just beneath the rim of the tank.
DRILLING THE BOTTOM OF A FRAG TANK
The placement of holes drilled into the bottom of your frag tank is entirely up to you, and what would be most suitable.
When using accompanying bulkheads, you are able to adjust the height of the inlet and outlet pipework, which pass straight through, before securing them at your chosen height at the bulkhead itself.
These heights are easily adjusted prior to the tank being filled, but cannot be adjusted thereafter. If you aim for similar minimum heights as detailed above you will find it works well.
Once again, if you are planning on including an emergency overflow, ensure it is just below the rim of the frag tank.