Hello there fellow sump builder

I'm in the middle of designing mine too, and every time I look at my rough draw I catch myself re-designing again LOL
There is no need for drilling holes into the sump tank. U can have the water go direktly into the first champer via pipes or hoses
What I would change about ur design is the size of the life rock chamber, there should be more surface are
IMO... maybe post meassurements
GOOD LUCK