korek. plus, 4inces high, 4 inches wide, medyo konti lang nadagdag sa water volume (minus LR at sand pa). kung sump, kahit balde, mas marami tubig.
yung balde or planggana, lagyan mo ng six inches ng sand, tapos LR. dun mo na lagay skimmer mo. screw type ilaw. ilagay mo near your tank, tapos pagawan mo ng lamesa or something, para di makita.
tama si chonglai, dont use foam, unless you clean it daily. ok na yung biological filter mo eh sump