Sorry to hear about your gramma. Did it show any signs of disease or parasites, or infection maybe? My chaeto mass floats but I have seen it sink to the bottom too. Little bits of my chaeto will spread around the bottom of the fuge and grow but I periodically scoop it up and reincorporate it into the mass. It shouldn't matter much though. Here is an article about the same type of fuge lighting that I use -
http://www.melevsreef.com/fuge_bulb.html
You can run chaeto on any sort of light cycle and it will be happy - reverse photoperiod, 24/7, or same photoperiod as your tank.