Looking for some low nutrient advice

[shakeandbake]

Got back into the game last July and working to slowly get running. Set up with dry rock and some sand that was wet, but not alive.

RSR 425XL, a RS 600 skimmer, refugium with chaeto, occasionally run carbon in a reactor off the manifold, 2 WAVs, and lit with a pair of Reefi Duo Ex. I have a DOS dripping roughly 20ml of Alk and Ca buffers and a DOS doing a small 12 gal a month water change.

Temp 78, Sal 34, PH 8.3, NO 0, NO2 0, NO3 5 ppm, Mg 1320, ALK 8.2, Ca 450, PO4 0

Livestock added over maybe 4 mos...2 clowns, 2 firefish, a dwarf angel, a bangaii cardinal and a royal gramma. CUC includes 2 cleaner shrimp, maybe 2 dozen snails and ~10 hermits.

Added a few test corals to the display maybe 3-4 months back after a QT. A frogspawn, a hammer, a torch and a handful of zoas. I also added a monti during that stretch. The monti lost color over the first few weeks and looked almost gone. So, I removed it, and added it back to the QT. The QT had similar parameters to the display, and tested 5 NO3, PO4 0.1 prior to adding back the monti. It runs an old 4 bulb t5 fixture. The monti has recovered nicely and it looks as good as it did day 1. However, the QT is now also testing 0 PO4 and showing diatoms.

The display tank did not really go through an ugly phase. The refugium had a bloom of purple and green slime that I expect was cyano. That ran itself out. For maybe 2-3 months the display has had on and off bouts with brown diatoms. The rocks have a few specks of purple coraline. Though the only source in the tank was a few small hermit shells, maybe a tiny circle on a zoa frag plug or two. So, I expected that to be slow in arriving.

Initially the LPS corals looked good. After a month they began to retract, and the LPS and zoas have not shown any real signs of growth since. I had the lights down for acclimation so I ramped that back up with no improvement. Currently I am running a lighting schedule that I downloaded from a user on R2R. Next, I thought perhaps the flow was too much so I backed that off, again to no improvement. Throughout I have been feeding relatively heavy. NO3 and PO4 haven't budged, pegged at 5 and 0. So I turned off the skimmer and kept feeding heavy. Nope. Then I got some Reef roids and fed 2x a week, spot/broadcast. Everything looked to appreciate that, but the FS, Hammer and Torch still remained partially retracted. This week I turned off the auto water change schedule and I picked up some Brightwell NeoPos hoping to raise PO4 manually.

I calculated based on 100 gal and dosed 15ml to raise PO4 to 0.04. I would dose before feeding and then test in the morning. Test consistently reads 0. So I would dose again in the morning and then test again at night before feeding. Still 0. So I recalculated to raise PO4 to 0.1 which came out to 38ml, so today I started dosing 30 ml.

Any advice? I suspect I just need to give it more time and that the PO4 is getting soaked up by rocks and livestock before it reads on a test. But the tank has had livestock and been fairly heavily fed for months. Feel like I have ruled out lighting, flow, and other parameters. But I am pretty green. Wanted some expert advice or opinions on strategy, especially before I leave the skimmer and auto water change off for any extended period.

Thank you for your time.

 

[Spare time]

I've been able to sustain low phosphates via daily feeding of reef energy and dosing phosphates to 0.03-0.05 (error range of 0.03 on the kit) if I see 0 when I test on the hanna ulr phosphate.

I would stop auto water changes. There is no need to do them if you have an effective method of removing waste products (carbon, refugium, etc.) and adding needed elements. You can always tune the refugium light down a bit.