Sps issues

[kwmcdani]

Red Sea 525+ – SPS bleaching / LPS decline despite seemingly reasonable parameters – looking for ideas

I’m looking for some outside input on a mixed reef that has been giving me problems since transferring everything from my previous tank.

My previous tank was doing very well with SPS, LPS, mushrooms/softies and anemones. It developed a leak around Christmas 2025, so everything was transferred into my current Red Sea 525+. The old tank was much simpler (no sump) and was running around 160 PAR in the SPS area.

Current equipment

* Red Sea 525+
* 2x Red Sea ReefLED 90 G1, approximately 9” above tank
* Current lighting: Blue 100%, White 30%, Moon 0%
* MP40: Low Reef Crest, approximately 3,118–3,290 GPH
* ReefWave 45: Random/Forward at 70%
* Vectra L2 return: currently 82W
* Aqua UV 15W running 24/7 on a dedicated ~210 GPH pump
* Skimmer
* Large chaeto refugium
* Filter sock
* Poly-Filter currently running

The refugium light had previously been running 24 hours/day. On Sept. 17 I changed it to 12 hours/day on a reverse light cycle because I was concerned I might be exporting nutrients too aggressively.

Current measured water parameters – Sept. 21

* Alkalinity: 8.5 dKH – Hanna
* Nitrate: 10.6 ppm – Hanna Marine Master HR
* Phosphate: 0.02 ppm – Hanna Marine Master
* Calcium: 509 ppm – Hanna (planning to repeat because previous measurement was considerably lower)
* Magnesium: not retested yet
* Temperature: approximately 78–79°F
* Salinity has been independently checked with both my equipment and at the LFS and has been consistent.
* LFS has repeatedly tested the water and says everything looks good, including no detectable copper.

Recent trends

Alk:
8.7 (9/7) → 8.7 (9/8) → 8.5 (9/21)

PO4:
0.03 (9/8) → 0.03 (9/16) → 0.02 (9/21)

Calcium:
435 (9/8) → 509 (9/21) — repeating this test.

Magnesium was 1540 ppm on 9/8, so that is also being repeated.

PAR

One fish-store SPS test coral has been kept at approximately 110 PAR.

A chalice is around 106 PAR.

Maximum PAR I’ve measured in the current tank is roughly 230.

I also recently obtained several SPS frags from another reefer. I personally measured his tank and most of those SPS were receiving 500–600 PAR, with some areas over 700 PAR. All of the frags I received came from near the top of his tank. Therefore even the highest locations in my tank are a major reduction in PAR compared with their previous environment.

What has been happening

Earlier in this tank’s life, I lost multiple SPS rapidly. Some would bleach/lose tissue within roughly a week. Torches/Euphyllia became progressively smaller, anemones nearly disappeared, while mushrooms and fish generally did considerably better.

One potentially important detail: early after transferring into this tank, the ReefLEDs were running 100% white for a period. That has since been reduced substantially.

Flow was also previously considerably higher. MP40 was around 3,744 GPH, ReefWave was 80%, and the Vectra was at 102W. I’ve since reduced all three. Some soft corals appeared to respond positively to the flow reduction.

Recently things seemed to stabilize. The inexpensive fish-store SPS at ~110 PAR survived much longer than previous SPS, and the newer donor SPS initially retained tissue.

Now I’m seeing SPS paling again.

The fish-store SPS that had been stable at ~110 PAR is developing pale/bleached-looking areas. One of the donor SPS is also becoming very pale/white at the upper tips. I’m trying to determine whether this is actual tissue loss versus severe bleaching, but the change is noticeable.

This is particularly confusing because the donor SPS came from 500–600+ PAR, while the fish-store coral is only receiving ~110 PAR. That makes simple excessive PAR seem less obvious as the common denominator.

At the same time, established LPS still aren’t showing the recovery I’d like, although recently added soft corals are opening/expanding.

Other troubleshooting already done

I discovered that filter socks had previously been washed in our household washing machine (with bleach cycles but the machine normally handles detergent), so I stopped using those because of the possibility of detergent/surfactant contamination.

I’m currently running Poly-Filter and UV. Water clarity improved dramatically after getting the UV operating properly, and visible cyano has disappeared.

I have considered sending an ICP test because I’m wondering if there is something we’re simply not measuring.

I also have an Orphek OR4 iCon UV/Violet bar on the way, but I do not plan to increase lighting aggressively while this is happening. I’ll PAR-map the tank before and after installation.

What I’m trying to figure out

With alk at 8.5, nitrate 10.6, PO4 0.02, stable temperature/salinity, relatively modest PAR, and SPS from very different previous lighting environments both beginning to pale, what would you investigate next?

I’m particularly interested in opinions on:

* PO4 being only 0.02 despite NO3 being 10.6
* possible trace-metal/contamination issue and whether ICP is warranted
* whether the high Ca/Mg readings could be relevant if confirmed
* whether the current flow could still be excessive
* anything else that could explain SPS + LPS problems while fish and mushrooms generally do well

I’m trying not to shotgun changes at the tank. I’d rather identify the most likely issue and change one variable at a time.

I think that’s enough detail that the experienced Reef2Reef people can actually troubleshoot it rather than giving you the usual “check your parameters” response. It also includes the odd part of this case: NO₃ is actually 10.6, so we’re not dealing with a generally nutrient-starved tank, but PO₄ is sitting very close to the floor at 0.02.