Hello,
Have a two-part problem;tank is 80g,has been on EI since set up 13 months
ago,has two cannister filters with a UV filter and 260w of light.I have recently
developed a severe problem with algae that looks like brown hair.I haven`t
changed dosing,every WC I remove nearly all of it and by next WC it`s back,a
lot!
The next problem is probably the cause(I think).Tank has a complete CO2
system purchased from on-line vendor with Milwaukee ph controller and external
reactor.PH is set at 6.2 but the ph never goes below 6.3 or 6.4,therefore the
system never shuts off.Stays on but ph doesn`t drop.This doesn`t make sense
to me with my limited experience.All help will be greatly appreciated.
Thanks,
Rich B.

It's a CO2 issue since EI rules out the nutrients. pH controller stinks due to the fact it assumes that the KH stays the same which might not be always the case. What is your KH by the way? I'll suggest you stop using the controller and just add CO2 during the day via a steady bubble rate and shut it off at night.

Regards
Peter Gwee