Need advice on water quality

[CGill311]

I'm having some trouble with my tank and was wondering if anyone could offer some advice.

A little info on my tank:
185 gal tank
65 gal sump
6x 5 ft T5's
Temp = 81-82
pH = 8.1 - 8.3
SG = 1.025
Nitrate = 0
Calcium = 420 ppm
Alk = 8-10 dKH (I dose two part every few days to keep the calcium and alk on target)

Tank inhabitants:
1 Purple tang
1 Naso Blonde tang
2 yasha gobies & pistol
1 black clownfish
3 blue reef chromis
5 anthias
1 McCosker's flasher wrasse
1 court jester goby
4 peppermint shrimp
lots of hermits and snails

One of my Scolys and one plate coral is receeding and I'm having some algae growth on the glass and some cyanobacteria growth in the tank. On the other hand, my other corals (montis, frogspawn, birdsnest, another plate, leather, etc) seem to be thriving.

Any suggestions?

 

[mutateddogbone]

how old are the bulbs and whats the location of the two receding corals in the tank and how much flow are they getting? do you ever feed the scoly or fungia?

 

[CGill311]

The t5 bulbs were new in March. The ballasts may be 5 years old or more. Both corals were on the sandbed. They were getting med/low indirect flow. I hadn't been feeding them. Recently, I've started spot feeding Hikari mysis to the other corals.

 

[CGill311]

The sandbed is 23" below waterline and bulbs are 7" above. Maybe just not enough light?

Can I borrow the club's PAR meter?

 

[Lytehouse]

Chris,

I would really check the mag

 

[mutateddogbone]

start feeding the scoly and fungia. they are low light corals and will benefit tremendously from feeding, especially in lower light like yours are in.

 

[CGill311]

Chris,

I would really check the mag

Checked the Magnesium today at 1100 ppm. I've got some Precision Magnesium to fix that. Does anyone dose other elements: Strontium, Iodine, etc?

I tend to do fewer water changes, skim wet, and use two part to keep alk and calcium on target.

 

[oddballs]

How long ago did the cyno show up? Also how much flow is in the tank,what and how many powerheads ? Also the algae on the glass what does it look like? Also what do you feed and how often? And last (for now) do you make your own water or buy from somewhere and either way what are the tds like in the water?