I oso dunnoe..I guess its because of my tank position in the house..the ceiling height is 5.52m..given hot air raises..so that area is especially cooling..not forgetting now is still year end/head period..shd see the temp raise to 28.5°c during mid year period..
Currently running wp40, skimz sk251, fluval sp6 & jebao dc6000..temp is at 27.1°c..