Lowering Phosphates Further After Algae Outbreak & SPS Death

[sgrosenb]

Hi all,

I'm wondering how best to approach lowering my phosphates in my tank now that an unfortunate algae outbreak and SPS death event has occurred. My tank is about 3 years old. My phosphates rose steadily over the past year or so to 0.2, at which point some of my SPS were still thriving and some were dying. I decided to lower my phosphates in an effort to have all my SPS happy. I used GFO and went what I thought was slowly, but clearly it was too quick. Over the course of about a month I lowered them from 0.2 to 0.07 or so, but after doing so I had a huge outbreak of turf algae (still fighting it to this day), and saw nearly all my SPS die (only have a few monti's left). I have about 12 fish in my 165 gallon and do not feed heavily. I also have a skimmer and chaeto in the fuge.

My phosphates are sitting between 0.07-0.1 and I'm wondering at this point, since all my SPS are dead, whether it makes sense to just run GFO somewhat aggressively to get the PO4 out of the rocks, sand, etc, or whether I should continue to take it slow. I'm not worried about killing more corals, I'm really just trying to get PO4 down to 0.02-0.03 and have it stay there (I'd love to be at the point where I'm dosing PO4 to keep it up).

I dose nitrates to keep them rock steady at 4-5ppm.

Once I get my PO4 down, I'd like to give it a few months and then start re-entering SPS into my tank.

Any insight would be helpful.

Thanks,
Scott

 

[Yazannreef]

Gfo will bottom out your phosphate if you use the right amount. I would suggest to keep it where it's at at 0.07 and plan on having nitrate around 7ppm .

Phosphates alone won't kill your corals in my experience. How is your Alkalinity? If there was a drastic swing upwards or downwards that's for sure will kill your SPS.

Also your salinity and temp playa a huge roll.

If you can keep phos/ nitrate/ alk/pH and salinity study I believe you will bounce back and keep the sps live and healthy.

I went thru a same issue. Dosing Gfo but I didn't realize my Alk was increasing rapidly for whatever reason and that killed some really nice sps I had.

 

[sgrosenb]

@Yazreef interesting you say that - thanks for the note. My alkalinity did rise, but only by about 1dKH over a few weeks. I know that's a large swing, but I've seen that before in my tank and it didn't kill the SPS. My guess is the GFO coupled with Alk rise really just nuked them.

I may not be thinking about it the right way, but I have in my mind that I'd like to zero out my PO4 and remove the "reserves" from my rock, sand, etc so that I can really start fresh and rather than fighting PO4 constantly, be in a position where I does it in order to keep it level.

Does anyone see any major issues in aggressively lower PO4 now that all my coral are dead, and then keeping things steady for a few months before re-entering SPS? My thought is that the biggest risk would be another algae outbreak, but with near-zero PO4, I would imagine at some point the algae gets suffocated out.

 

[homer1475]

One word.....

Dinoflagelettes.

Only reason I would never bottom out nutrients.

Whatever killed your SPS, it was not the .2. I purposely keep my tank between .1 and .2 Sometimes even as high as .3. Have no issues with SPS.

 

[sgrosenb]

Thanks @homer1475 - I don't think it was the 0.2, but rather my rapid decline of PO4 and usage of GFO from 0.2 down to 0.07. My tank was humming along for 1+ years with no issues and within a few weeks my SPS died; the only variable I changed was adding GFO.