Did an overpowered refugium Light RTN my SPS?

[Pico Keeper]

I'm fairly sure I know what happened but I want to bounce my theory off of a few people so I can learn from my mistakes.

Tank Background: I have a 90gallon that is mostly LPS, zoas, and a few montis. It's 50-days old for me but was established rock and system before I got it so I would consider it matured to at least the 1-year mark, frags are all mostly new 15-30 days..

Baseline Parameters:
100g total volume, 90g display, 20g water changes weekly with HW Reefer Salt
Decent sized refugium.
SG - 1.026
Alk - 9.0
Calc - 420
Magnesium - 1360
Nitrate - <1
Phosphate - This is what we're going to discuss..

The tank has a normal bioload, nothing crazy. I feed the fish and corals a normal amount, about 1 cube/day plus some Reef Chili or Reef Roids EOD. I also dose KZ Aminos, Sponge Power, Coral Vitalizer, and Pohls Extra about half of the recommended dosage as instructed for each.

Here's what happened.

The tank had zero algae, zero nitrate, but would test .1 Phosphate on the Hanna ULR Phosporus checker. I was unsure why the phosphates would be so high but it made me think we were outside the accurate range of the checker. Either way I wanted to get phosphates down so I bought a really powerful 300W Mars Hydro Grow Lamp to light my refugium with.
https://www.amazon.com/MarsHydro-Spe...rds=mars+hydro

It worked like a charm and got my phosphates down to .02 in the course of 10 days. It also completely filled my refugium with dense crazy amounts of chaeto. After those 10 days passed, I harvested about 90% of the chaeto and left 10% to seed. A few days later I saw the light spill from the lamp was causing some nuisance algaes to grow in my return chamber. Out of curiousity, I tested phosphates again and they had jumped back up to .09 which kinda freaked me out. The day I tested was water change day so I didnt worry too much as the tank looks phenomenal at the moment and I knew I was going to knock that number down by at least 20%.

Did my water change, life went on... Chaeto was growing extremely fast and maybe 6-7 days after initial harvest was getting pretty big again. BUT. It doesn't spin in the refugium, only the top gets light. So last night before bed, I grabbed the entire bed of chaeto and flipped it over so the darker part got some light too. I'm 75% sure flipping the chaeto caused my issue. The next morning everything looked great but my green monti cap had RTN'd a section over night. I tested phosphates on the Hanna ULR checker, it was 1ppb. I re-did the test to double check, this time it read 0. Uh oh.

My theory is that flipping the chaeto over last night caused a growth spike due to the intensity of the grow lamp. Sucked my phosphates to zero and caused the Monti to RTN. Just in case I pulled it out, dipped it in coral RX, inspected for nudis or other pests, but found absolutely nothing. I'm gonna clip away the dead section and im guessing it will bounce back. But I'm curious if my theory is valid. Can an overlit refugium and chaeto crush phosphate levels so low that SPS corals RTN overnight?

Here's the tank this morning, sump showing the light on, a pic of the RTN'd montipora cap and a small video I made for entertainment purposes.





https://youtu.be/h0br3AEPUhc

[scuzy]

What's your lighting cycled on the fuge?

[mcgyvr]

I highly doubt it..

[shiftline]

I'm going to guess no. If you are running a fuge and GFO you mag have stripped out all your phosphates 0 phosphates is bad! You need some and I have only ever seen sps issue from using too much GFO. Never to much Chaeto. On a side note I think I have that same fuge light (it's awesome!)


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[Pico Keeper]

Originally Posted by scuzy

What's your lighting cycled on the fuge?

It's on for about 14 hours total. It turns on 1 hour before lights go out, and turns on one hour after lights turn on..

[Pico Keeper]

Originally Posted by shiftline

I'm going to guess no. If you are running a fuge and GFO you mag have stripped out all your phosphates 0 phosphates is bad! You need some and I have only ever seen sps issue from using too much GFO. Never to much Chaeto. On a side note I think I have that same fuge light (it's awesome!)

The tank had no GFO. I dont think too much chaeto was the issue, I thought my chaeto growing too fast was the issue. When I cut it down to a ball it only took 4-5 days for it to quadruple in size or more.

[karimwassef]

No. That's not your problem. Check your Alk.

You seem overly obsessed with P. If your tank is healthy and you're feeding without algae, don't worry about it.

I run my scrubber/fuge for 21 hours a day lit with 600W of LED... just makes pods to feed the corals.

[Pico Keeper]

Originally Posted by karimwassef

No. That's not your problem. Check your Alk.

You seem overly obsessed with P. If your tank is healthy and you're feeding without algae, don't worry about it.

I run my scrubber/fuge for 21 hours a day lit with 600W of LED... just makes pods to feed the corals.

Hmm. Ok fair advice. I just was thinking that stripping phosphates to zero can hurt corals like when people use too much gfo or lanthanam chloride. I guess it was just a random rtn then?

Alk has been at 9.0 - 9.1 for last 3-4 weeks. Tested daily. Alk/Calc/Mag are on point as I was tuning in the dosing pumps while adding corals simultaneously and was constantly adjusting things to keep them perfect.

[karimwassef]

Alk can vary throughout the day. All it takes is a single high spike to cause damage IME.

La or GFO are chemical, not biological. LaCl will actually deplete alkalinity too.

Algae growth could reduce CO2 increasing pH and that could have messed with your alkalinity, but it would have been a soft change unless your dosing coincidentally caused a sharp increase for a short period.

I just don't think algae will remove P at a rate that causes coral death. Something else broke and the timing was coincident.

[Pico Keeper]

Originally Posted by karimwassef

Alk can vary throughout the day. All it takes is a single high spike to cause damage IME.

La or GFO are chemical, not biological. LaCl will actually deplete alkalinity too.

Algae growth could reduce CO2 increasing pH and that could have messed with your alkalinity, but it would have been a soft change unless your dosing coincidentally caused a sharp increase for a short period.

I just don't think algae will remove P at a rate that causes coral death. Something else broke and the timing was coincident.

Oh, man, that makes me ask so many more questions about what went wrong. Im going to have to go back to the drawing board, or just chalk it up to an unknown mistake and move on. But I'd love to figure out why that coral RTNd like that. The PH stays pretty constant overnight and doesnt swing much with the current refugium light cycle.. Pretty consistent 8.1-8.2, it slowly rises as it gets closer to the morning to 8.3. Allk/Calc are dosed 24hrs a day with a doser.

[karimwassef]

Take a day and measure your Alk every 3 hours... I measured mine every hour and I was surprised.

[Pico Keeper]

Originally Posted by karimwassef

Take a day and measure your Alk every 3 hours... I measured mine every hour and I was surprised.

Okee Dokee, will do that soon and see how it goes.