I just don't know what to do anymore.
I am sick of pulling 3 cups of thread/beard algae a week from my tank.
Does anyone have a clue as to what I can do to solve this problem?

75 gallon planted tank.

pH - 6.8
kH - 4.5
gH - 5
Temp - 77

DIY CO2 Injection through a motorized homemade diffuser.

4 x Philips T32 850T8 bulbs for 10 hours a day in homemade hood with
reflector. (12,000 lumens) (Was 12 hours, but I cut back to try to
reduce algae growth.)

Variety of plants, including hairgrass, various crypts, a piece of
hornwort, clumps of bacapa & loosetrife, several different swords,
All plant growth is good, although the anubias was slightly yellowing
so I ammended one time with a small amount of SeaChem Fe.

When the tank was first set up, everything was fine, but for the past
6 months, I just can't keep the algae under control.

I've added SAE's, mollies, platies, and otto's but they can't keep up
with the massive growth. Sometimes, it's so bad it clogs the intake
on the CO2 diffusion pump.

Total fish load is light - 5 cardinal tetras, 5 head & tail lights, 2
adult platies, 3 juvenile platies, 1 adult molly, one juvenile molly,
3 ottocinclus, 2 SAEs, 1 corydoras julii and one black loach.
(Yea, I know - they want some company...)

Added fertilizers (SeaChem Flourish), stopped adding ferts, etc.
I've done repeated weekly 50% water changes.
The only additions I have made to the past few water changes has been
epsom salts, baking soda, and calcium carbonate to harden the water.
Nothing I do even slows the proliferation.

When I lived in Florida, I kept reefs tanks. When I began using R.O.
water, my problems with algae disappeared. Could it be nasty tap
water causing this?

I started this planted tank because I thought it would be simpler than
a reef tank. HA! That has NOT been my experience...

Any Ideas?

Greg