Need help understanding and managing increased phosphate

[DavidA]

OK, I officially need help understanding and managing my phosphate levels. I posted a few days ago and at the time I was only "curious" because all reef citizens (LPS, leathers, monti, clams etc) were thriving and I thought my management plan of replacing exhausted GfO every 3 days was slowly working. I now need help understanding what is happening and what to do. The reef inhabitants continue to thrive but phosphate levels are back up to .63 after dipping to .3-.5 The graph below depicts Hanna ULR phosphate levels over time. Phosphate levels were stable between .1-.2 for months. On January 17th phosphate was .12, on January 18th it was .35 on January 19th .53 and on January 21 it was .69. In short, it spiked from a steady baseline to .7 over days. The spike did not coincide with a new box of reagent.

My mixed reef (photo below) is a Nuvo 40 long AIO with large leather corals, healthy LPS (goniopora, duncan, candy cane, torches, hammers, octospawn, favia, acans, microsusa), GSP, xenia, derasa clam, clean up crew, a few monti pieces and 7 fish (starry blenny, 2 clowns, hectors goby, neon cleaner goby, royal gramma and biota mandarin). It is 7 months old and was established with Gulf Live Rock and sand plus Australian live rock. Nitrate runs 10-15 and was 12 this morning with a phosphate of .63.. Alkalinity averaged 8-9 with AFR before the spike. Since the spike, it runs 7-8 with AFR plus supplemental Brightwell KH when I change GFO. I do not have algae issues.

At the time of the spike nutrient export included thick blue filter pads (changed or cleaned daily), IM protein skimmer, thriving chaeto refugium and weekly 10% water changes. Nutrient addition consisted of 1/2 cube of mysis or brine/day, benepets powder 3/16 teaspoons weekly and algae pod pate 1/8 teaspoon twice per week. A few weeks prior to the spike I began dosing Ocean Magic 25 ml/day in anticipation of promoting pod growth for the addition of a Mandarin. I thought I would be safe dosing phytoplankton because I was checking phosphate daily. I stopped the filter pads last week because I dont want to remove pods (other than protein skimming). I stopped phyto dosing when the phosphate level increased. I also stopped benepets powder and pod pate after the spike but added 1/8 teaspoon per day of TDO pellets for the Mandarin (target fed). I continue to perform weekly 10% water changes along with protein skimming and the chaeto refugium (harvested every 3 weeks or so).

Immediately after the spike I could not find dead organisms or dead spots and the chaeto was bright green. I thoroughly cleaned the display tank, sump, pumps and skimmer. Given the phosphate spike exceeded my target of .1-.3 I began dosing 5-6 tablespoons of BRS high capacity GFO in a reactor on January 21. I have run GFO continuously since then. The GFO exhausts after 48-72 hours and I have gone through about 2 pounds of high capacity GFO since the January spike. Despite 2 pounds of high capacity GFO over 2 months, levels remain well above my target of .1-.3. I know the reactor is working because I check KH and phosphate daily after refreshing GFO and KH and phosphate both drop the day after changing media but phosphate goes back up by day 3. I adjust the reactor to achieve shimmering movement of the top particles. I have also used GFO in media bags and the media still exh

I will summarize as follows: 2 months ago phosphate levels spiked over 3 days from a steady baseline of .1-.2 to .69 with steady nitrate levels of 10-15. Nothing changed to account for the spike except some dosing of phytoplankton (long since stopped). My export regimen of skimmer, refugium, water changes and carbon seems reasonable for my feeding schedule (basically 1/2 cube mysis plus 1/8 teaspoon TDO pellets and occasional benepets). Despite 2 pounds of high capacity BRS GFO over 2 months phosphate level this morning was .63. My chaeto remains bright green with no evidence of die off and I harvest it every 3 months.

Help! Why is my elevated phosphate so stubborn? What should I do?

 

[Randy Holmes-Farley]

Assuming you are not using tap water or a depleted DI with Ro/DI water, any phosphate added to the tank in foods, which always have a lot of N and P.

A sudden spike in P and not N might be test error, or perhaps something very large died, but it is not an ordinary event, especially without an N rise. If N bottoms out, organisms may then not grow well and phosphate uptake will decline.

There's no evidence that 0.63 ppm phosphate is a serious issue, so don't agonize over it. Some great tanks have 1+ ppm phosphate.

These have more, with the first one the most recent and discussing tanks with 1+ ppm phosphate:

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

Phosphate In The Reef Aquarium

Nitrate in the Reef Aquarium - REEFEDITION

 

[KrisReef]

Totally agree with Randy. I suspect that more tanks have been ruined or died from efforts to lower phosphate numbers than almost any other "intentional fix" issue in this hobby. Lowering P has been attempted by carbon dosing, (biopellets, vodka, other C sources), by GFO and lanthanum chloride reactions, water changes, live rock changes, so many schemes and frustrations because of an opinion that it should be detected at a certain, usually arbitrary (low, medium, high) level to satistfy the community that a tank is as healthy as can be.

I'm late for an appointment, sitting here unclothed and angry thinking about the strange power of phosphate levels to command so much attention of folks in our hobby.

Triple rinse your cuvette with RODI water after every test to keep the glass clean.

 

[DavidA]

Assuming you are not using tap water or a depleted DI with Ro/DI water, any phosphate added to the tank in foods, which always have a lot of N and P.

A sudden spike in P and not N might be test error, or perhaps something very large died, but it is not an ordinary event, especially without an N rise. If N bottoms out, organisms may then not grow well and phosphate uptake will decline.

There's no evidence that 0.63 ppm phosphate is a serious issue, so don't agonize over it. Some great tanks have 1+ ppm phosphate.

These have more, with the first one the most recent and discussing tanks with 1+ ppm phosphate:

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

Phosphate In The Reef Aquarium

Nitrate in the Reef Aquarium - REEFEDITION

Thank you Randy. Very reassuring, particularly since the reef is doing well. I am still having trouble understanding what is going on though. My phosphate input and export appears to be in approximate equilibrium which means the food I am adding (1/2 cube mysis and 1/4 teaspoon TDO pellets) is being matched by 6 tablespoons of high capacity GFO every 3 days plus protein skimming, growth of corals, weekly water changes and chaeto. Could this amount of food possibly match this amount of export?

I do use RO/DI water with 0 TDS and 0 measured phosphate. I described the initial increase as a spike but a better description is an abrupt increase in average phosphate from .15 to about .5 without any obvious changes in added food or nutrient export.

 

[Dan_P]

Thank you Randy. Very reassuring, particularly since the reef is doing well. I am still having trouble understanding what is going on though. My phosphate input and export appears to be in approximate equilibrium which means the food I am adding (1/2 cube mysis and 1/4 teaspoon TDO pellets) is being matched by 6 tablespoons of high capacity GFO every 3 days plus protein skimming, growth of corals, weekly water changes and chaeto. Could this amount of food possibly match this amount of export?

I do use RO/DI water with 0 TDS and 0 measured phosphate. I described the initial increase as a spike but a better description is an abrupt increase in average phosphate from .15 to about .5 without any obvious changes in added food or nutrient export.

The aquarium is not a machine with nutrient cycles that can be easily if ever understood. Since your system is new, its nutrient cycles are more likely to exhibit chaotic behavior than older systems.

It sounds like your are rigorously managing your system. Fantastic! You are doing the right thing. Don’t stop doing this just because the aquarium is not quite as deterministic in its response to your excellent care. Treat it as a puppy. It’s going to pee on the carpet and chew your shoe to shreds. It will settle down in time, though you won’t understand why.

 

[DavidA]

D

The aquarium is not a machine with nutrient cycles that can be easily if ever understood. Since your system is new, its nutrient cycles are more likely to exhibit chaotic behavior than older systems.

It sounds like your are rigorously managing your system. Fantastic! You are doing the right thing. Don’t stop doing this just because the aquarium is not quite as deterministic in its response to your excellent care. Treat it as a puppy. It’s going to pee on the carpet and chew your shoe to shreds. It will settle down in time, though you won’t understand why.

Dan, thank you! Extremely helpful reminder beautifully expressed. Intellectually I know that a reef aquarium is a "complex adaptive system" like the weather consisting of a web of interacting inputs and outputs. But in practice I forget the complex web and expect outputs to be perfectly and linearly predictable from inputs. Not true for puppies. Not true for kids. Not true for grandkids. Not true for weather. Not true for adults. Not true for the human body. And definitely not true for our home made reef environments.