in the mean time while waiting for the cement to set... remeasure the lenghts of the pipes to make sure you got the right lenghts.... there's no room for mistake here or else you need the buy new sets of elbows and pipes... LOLZ!!
then start with the skimmer:
I measured the bigger pvc where the tip should level with the desired water level in the tank.. coz i don't want to see the water level below the glass rim.
cut the bigger pvc and install the end cap. After getting it fixed. lets start the teeth of the overflow skimmer.
using the reducer,
the one on the left...coupling is the one on the right.