Had my H380 light over the fuge about 8 months and it grows cheato like crazy. When it is gets too full I also see the top layer turn white. I did what Randy says and cut back the light a little less on time since I cannot raise it any higher due to the stand height. However, when it gets too full it is time to harvest. Love this light! I would say over the past 8 months I have traded in about $100 worth of chaeto to the LFS for merch. In more time or if I had a bigger fuge this thing will pay for itself!