For those interested in following the events related to my 480g project, take note that I sometimes write stuff on ReefCentral that I do not repeat on here. So feel free to visit my thread there.
Actually I was slightly wrong with my observations. The pipe leading from the overflow to the skimmer was actually inclined away from the skimmer - a couple of degrees...
I removed 32mm of wood from the skimmer's base support and replaced it with 25mm polystyrene. It seems as if I have a slight downward slant now. Will start the circulation back up in an hour's time.
Yesterday evening I could not wait longer. At midnight I needed about 40l of water to close the loop. That takes about 2 hours to make, so I decided to go to bed instead.
This morning I filled the remaining water and voila - everything worked. No leaks (touch wood). However my durso standpipe was not working. Water was oscillating up and down vigorously. I decided to remove the top and cut off a 4cm piece to lower it (it was too high). Since I dread leaks I cut it in place - and did not remove the pipe from the overflow.
Once cut, I placed the durso head back but no luck - same thing.
One aspect of autumn that really captures my attention is the spectacular scenes the combination of a changing sun and the falling coloured leaves of trees produce.
Some quick equipment shots from yesterday: