As what i have observed, mine BK skimmer is the internal version, it require a constant water level to work efficiently. For the past 2 days (Doze Zevoit Coral snow on sunday, 1230am), skimmate seems more. By right as the water level in the sump falls, the foam level at the neck would drop unless i adjust the riser tube thus skimmate collected in the cup would be lesser.
if you would to compare with the previous 2 x pics of the skimmer, there is a definite increase in the skimmate.