Drilling a tank

[Farrmanchu]

IMO an external overflow box is the way to go. It doesn't take up tank space. You can use the Dremel bits to notch out the top edge of the tank, whatever length and depth you need (depending on amout of flow). Eggcrate or Mesh covers the "notch", it functions the same as an internal overflow, with no risk of syphon loss that can happen with a HOB overflow. I'll try to find a good link.