i prefer doing 10% wc every week rather than using yung mga GFO, rowaphos at phosgard. For a small tank, 10% weekly WC is the best at hindi pa ganun kasakit sa bulsa dahil maliit lang rin yung 10% na yun.
May naririnig ako from experience ng ibang friends na pag sobrang bilis ng pag absorb ng mga ito(GFO, rowaphos or phosgard), nastrestress rin yung mga corals. kunyari 40 nitrates, then bukas 0 agad. Sample lang yan, medyo exaggerated lang pero anything na sudden change will cause stress sa LS natin. HTH