0 nitrates, brown/cyano algae?

I would say your bulbs are getting near to be needing replaced. bout 1 year
all any bulbs good for.
Ive even heard of people changing out there bulbs every 6 to 8 months to continulay have a good spectrum.
How big the tank ?
Also would perform a water change at least every 3rd or 4th week.
it will help in keeping PH up and helps with reducing nitrate/phosphates.

 

Tank is 90 gallons with 44 gallon sump.

 

how much should I be feeding?

 

You've got a good size skimmer (supposing it's working right), a big sump/fuge, and good flow. I can see that the flow and skimmer keep the nitrates down to 0ppm. That's what I've always been reading since my cycle was over. How much live rock and live sand in there as a natural filter? I agree it could be the lights. How long are they on, what type bulbs, and how old are they. You can add phosban or phosguard (use ~ 1-1/2 cups phosguard in a nylon sock for your 90+44 gal system). Even with a phosphate test, some algaes (cyano, etc...) will use it up as soon as it is in the tank, and therefore it's undetectable. So test your water source for phosphates, that's what I did. I found out the tap water I'm stuck using (for now until I win the RO/DI) does have a very small amount of phosphates, but other than that, very clean and pH of 8.3. I haven't tested my tap water for some of the other hard elements in the water yet, but will sometime soon.

 

oh you got that in there, while i was typing, I would certainly agree on that
Mission.
How bout one cube per every other day ? i would suggest, you'd be supprized at how well they do and some of that hair algae will disappear.
how bout increasing the number of tank cleaners as well ?

 

As far as feeding goes I only feed food that can be consumed in less than 10mins time. About 1 every other day. A cube a day is definitely overfeeding in your case. And that frozen stuff contains lots of phosphate.

 

How big are the fish?

 

Don't laugh. I have a bicolor pseudochromis, oscelaris clown, cleaner shrimp, candy cane coral, a few zoas, xenia, peppermint shrimp, 10lbs of live rock, 5 turbo snails, 5 hermit crabs, and a partridge in a pear tree.