Not quit sure what you mean by levels... But I just put the taller ones in back. And then I keep cutting the stem plants to the size I want them to be.
Well the maintance is a 20 - 25% water change weekly. Then Every other week I prune all the stem plants. And clean any algea growth off the front and sides. And about once a month I remove any dead or dying leaves. I add co2 with a yeast bottle that I change every two weeks. I clean the filter once a month. feed the fish every other day. Change the lights every 9 months. add fertilizer tablets every three months and liquid ferts every 3 days.