Diatoms old lighting?

A diatom bloom 2 and half years later? Nitrates are ~0, no ammonia, been running phosban reactor for a week and diatoms are still there, use RO/DI, Red Sea Coral Pro salt, lighting is 2 150W 14k phoenix w/ 4 39W T5 actinics. Could this bloom because of the age of the MH bulbs, they are going on 8 months? I will change soon anyway. How often should actinic T5's be changed? Oh, and I run UV as well.

 

Maybe the Bulb in the UV unit is bad...If it solved it in the begining and now the issue came back id be willing to bet that, and possibly old bulbs are contributing factors.

 

I doubt its the bulbs. I don't thin they're tat new, but im not sure.

 

could be silicates or maybe getting false readings from diatoms using nitrates and phosphates. I still have traces in my tanks and just thought it was good to have a small amount.

 

How old are the T5's? What brand bulbs? Generally, MH's and T5's should be replaced every 10-12 months

 

How old are the RO/DI filters?

 

Just put in a new UV bulb, the RO/DI unit I received for christmas this year, the T5's are by current, they are the original bulbs that came with the light fixture, about 8 months old. The halides are newer, I bought them to replace the crappy ones that were in there