The soft tube is just another kind, no bubbles in there.
Using a ball valve to close the tyre-tube after filling the system.
Water starts to get distributed.
Using an external, old AT PSU to engage the pump.
OK, water is flowing and there's no leakage.
The tube on the intake side of the pump is slightly bent due to the tension. Fortunately this doesn't affect the flow considerably.
But something's not right, there're far too many bubbles in the water.
The CPU cooler with the intake on the left side.
The production of bubbles became worse.
After several hours of operation I decided to place the equalising reservoir at the highest point of the system in order to get rid of all the air in the loop. The result didn't turn out very beautiful, but at least it serves the purpose.
Complete view. Mind the clarity of the water.