Looking for some new suggestions on the tank

[91sbcamaro]

I would like some new suggestions on getting rid of the re-occuring brown algea as well as an overall tank remodel.

Background:
Tanks has been up and running for 4 years, always had slow coral growth. Everything is alive just low on colors and slow growing.

75 Gallon, 20 Gallon Sump w/ Skimmer

Temp: 77.4
PH: 8.45
Mag: 1600
Cal: 420
Alk: 9.5
Phosphate: 5ppb (.005 ppm) seems low checked with hanna tester
RO/DI water at 3ppm w/ water changes every 2-3 weeks

Photos below:

Color may be a bit off since these were taken from my phone, the picture of the powerhead is brown algea, the rocks have a film on them and not much of any color to it.

 

[Reef Frog]

I would scrape the coralline algae off the back pane and perhaps do a black bachground. The rock work looks nice to me. It looks like you still have plenty of real estate for more coral.

 

[toothman]

Even though you have some algae it looks to sterile to me. (possibly dosing vinegar) I think my tank needs to have some nutrients to grow dark rich colored coral that grows quickly. I think there should be some nitrate in the water 2-5 ppm, phosphate matters also it is like a sweet spot you need to find for optimal coral growth. Your tank looks a little too nutrient poor. My suggestion is to add another fish or 2 a nice blond naso tang or sailfin tang would be nice. As far as algae, some is good, rely on residents like emerald crabs to pick at the rocks and a sea urchin. Urchins are a great general cleaner. My tank looks best and grows best when it is at 15 ppb with hanna, my tank varies sometimes it is 2ppb and sometimes it is 20 ppb. With the hanna 713 however it will test 0 with 736 it tests like 15ppb. I do not think the 713 is accurate, using faunna marin reference water for comparison.

 

[reefsahoy]

I would bet you're dosing some form of carbon. When I did, I had that same fuzz looking hair on the rocks.

 

[rsaha]

I would scrape the back for sure. I would also be looking hard at why growth is slow.