In a tank with 160 watts over 50gallons 36x18x20 planted heavily with Rotala Macranda green (Narrow leaf), Limnophila aromaticoides, Rotala Rotundfolia sp. green, Heteranthera zosterfolia, Echindorus tennelus Micro, Eusteralis stellata broad leaf( Actually one stem but hoping to have more soon. How often should i expect to add these. I really have absolutly no idea whatsoever. I just need a ball park so i can narrow it down from there in experimentation. Light fish load too that doesn't get fed (Algae eaters). Tank is fully fertilized heavily through water column. Plants prefer to tank out of the water column but the addition near the roots seems to help.