I was reading about lotus because I lost a few this year and began searching. One thing the stuck out like a sore thumb is the I may have had too much water over the tubers. Perry Slocum only alows 3 ins in his pots when planting for water. Lotus is a bog plant and not a deep water plant. It needs 75-85 degree temps for growth and to produce blooms.
I dumped some of the water out of my pots leaving only 3-6in of water and noticed a quick difference in the response of the lotus. They began throwing up more shoots, I am seeing some buds... they just look happier. * Lotus Smiling*
The ones I lost may have died from not getting enough heat sunlight. I had also placed some duckweed and azolla (sp) in the tops of some thinking it would help with algae, but I think it just helped keep the water cooler. Learning as I go.
"Maintenance
During the growing season
Once a lotus bloom drops it's petals, dead heading (removing the spent flowers and stems) of most varieties of lotus will prompt it to re-bloom.
Fertilize monthly, but don't over fertilize.
Remove aging leaves, being careful to cut the stem above the water line.
Ensure a constantly moist growing condition, but never more than 6 inches of water over the soil where the lotus is planted."