How to reduce 5.6ppm Phosphates (NOT .56)

[Broadwell]

I have a 210G FOWLR with very high phosphate levels. Nitrate is currently 56 and phosphate is 5.6. I have confirmed these numbers with multiple test kits including Hanna testers. With a FOWLR tank, I have heard that high phosphates are not that toxic but the current levels still concern me and I would like to reduce the phosphate levels. If possible, to a level where I am comfortable putting inverts/CUC and maybe even corals into the tank in the future. Any advice or help is very welcome! It has been very difficult to find previous records of what to do because when people say "high phosphates" they are usually talking about <1ppm on this site.

Context:
I got the tank from someone about 6 weeks ago and took the whole system with fish. The water started with nitrates in excess of 300ppm and phosphates in excess of 8ppm. When rehoming the system, I did my best with the stress of having to quickly redo the plumbing and make a new stand because they fell apart when moving. I rinsed the old sandbed thoroughly and reused it. I was worried about the amount of beneficial bacteria available so made a mistake and used approx. 10-20% of the old tank water and approx. 40 pounds of the old live rock in the system (along with ~150 pounds of new dry rock). I have had the tank up in my house for ~6 weeks now and it is time to seek help for phosphate reduction. For the record, I have two other successful tanks with ~10 nitrates and ~.1 phosphates and I know my newly mixed saltwater (IO Reef Crystals) is not the source of any problems.

Livestock:
1 French Angelfish
1 Purple Tang
1 Blue Hippo Tang
1 Naso Tang
1 Goldrim Tang
1 Lieutenant Tang

Parameters (all Hanna testers):
Ammonia: 0
Nitrite: 0
Nitrate: 56ppm
Phosphate: 5.6ppm
Ph: 7.7-7.9 (I would like this somewhat higher; I might try a CO2 scrubber and see if that helps. Once I get a refugium working, that should help too)
Salinity: 1.025
Temp: 88F
Alkalinity: 9.5

Possible Solutions:
Protein Skimmer: I have a Reef Octopus Classic 202-S that is working well in the sump. I will keep this running 24/7 but I definitely think I need additional methods of phosphate reduction.
Refugium: After a long delay of my macro order, I recently got some Ulva which I have put in the refugium chamber of my sump. As of now, I don't really know how it is doing since I put it in just a day ago. I hope this will help export nitrates and phosphates over time but I also worry that the very high phosphate might kill this outright (is this a stupid thing to think?)
Water Changes: After the initial ~80% WC, I have done 3 25% WCs and a few smaller WCs. This has worked well in reducing nitrates but not really phosphate. I imagine there is a large amount of phosphate leeching out from the old live rock I used. It is difficult for me to change more than 50 gallons of the water at a time (25%) because of the limitations of my RODI & mixing setups. Maybe I should just keep doing 25% water changes weekly and see what happens, though this would probably take a long time to reduce the phosphate to a palatable level?
Live Rock: I used ~40 pounds of live rock from the old (stinky water) system along with ~140 pounds of new dry rock. At this point, would it help to remove the old live rock which is probably leeching phosphates? Or does all the immature dry rock now probably have that same amount of phosphate ready to leech out?
Lanathum Chloride: This seems like the only fast solution to getting the phosphate down to manageable levels. I have already purchased Phosphate RX and 5 micron filter socks. Before I was going to dose, I did some more research on this and it seems there are MANY anecdotal accounts of Yellow (or more broadly, Zebrasoma) Tangs dying when dosing this. I was wondering if any more research has been done to figure out whether the unbound LCl or the phosphate-bound LCl precipatate is actually killing the tangs. If it is the former, I probably won't have a problem because of the insane amount of phosphate. Regardless, I am currently too scared to dose any of this lest I kill or hurt any of my tangs, especially the purple tang. This still might be the best option, but I REALLY don't want to hurt my fish.
GFO/Phosban: Please excuse my ignorace as I have never used either of these or even a reactor before. I think these could work, but it would probably be a very long process and expensive due to the amount of substrate required? I actually have an unused Reef Octopus BR-MF-140 sitting around, but I don't think GFO or phosban would work in this because it is designed for biopellets?
Tank Breakdown: Is this a level of phosphate where I should consider breaking down the tank and starting over with completely new water? Hopefully I don't have to do this :(

Thank you so much for anyone who took the time to read all of this. I know I have made some mistakes during this process but I appreciate any help or feedback!

 

[Pistondog]

As you suggest, lc is your best option.
Best practice is to:
1. Dilute 50:1 with rodi
2. Drip 1 drop per second max
3. Drip into overflow
4. Catch with 5 micron sox
5. Run a skimmer

I would have a couple sets of sox as they will clog and youll need to switch out or stop.
Itll take a while as phosphate also binds to rock and sand, and releases in equilibrium with the water.
There are some theories as to the mechanism of injury. One is that the flocculant might dissolve in the acidic area of gills, allowing the free lanthanum to react locally, injuring/killing the fish. May or may not be the case.
The guidelines above are intended to minimize the flocculant that gets into the display tank.
I have a yellow tang and have used lc many times over the years.

 

[Broadwell]

As you suggest, lc is your best option.
Best practice is to:
1. Dilute 50:1 with rodi
2. Drip 1 drop per second max
3. Drip into overflow
4. Catch with 5 micron sox
5. Run a skimmer

I would have a couple sets of sox as they will clog and youll need to switch out or stop.
Itll take a while as phosphate also binds to rock and sand, and releases in equilibrium with the water.
There are some theories as to the mechanism of injury. One is that the flocculant might dissolve in the acidic area of gills, allowing the free lanthanum to react locally, injuring/killing the fish. May or may not be the case.
The guidelines above are intended to minimize the flocculant that gets into the display tank.
I have a yellow tang and have used lc many times over the years.

Thank you for the feedback. I dont exactly have an overflow that I can easily drip into. Can I just drip into 5 micron sock in sump?

 

[Pistondog]

Thank you for the feedback. I dont exactly have an overflow that I can easily drip into. Can I just drip into 5 micron sock in sump?

You want to maximize lc contact time. how does water get into sox?

Edit: is there an underwater drain?

 

[Broadwell]

Thank you for the feedback. I dont exactly have an overflow that I can easily drip into. Can I just drip into 5 micron sock in sump?

You want to maximize lc contact time. how does water get into sox?

Edit: is there an underwater drain?

I do have an underwater drain. I might be able to drain some of the water and then dose into it

 

[Pistondog]

I do have an underwater drain. I might be able to drain some of the water and then dose into it

Thats a lot of work. Drip into the sox, should be ok.

 

[Broadwell]

I do have an underwater drain. I might be able to drain some of the water and then dose into it

Thats a lot of work. Drip into the sox, should be ok.

Thanks for the advice - for the record, how bad is 5.6ppm phosphate? Should I be worried about the fish if I dont reduce it quickly?

 

[Gjedde]

I had 2.4 in my reef. I lowered it over 3 weeks using lc in my filter socks. At .15 now with gfo in my drain chamber.

 

[Miami Reef]

It isn’t known whether soluble lanthanum vs precipitated lanthanum is the issue.

I would start slow. The issue seems reversible if you start slow and stop immediately after fast breathing occurs.

 

[Pistondog]

Thanks for the advice - for the record, how bad is 5.6ppm phosphate? Should I be worried about the fish if I dont reduce it quickly?

Sorry, i dont know.
Maybe @Jay Hemdal can help.

 

[Miami Reef]

@Randy Holmes-Farley

What do you think about 5.6 ppm PO4 (yes, 5.6 ppm) for fish-only tanks?

 

[Jay Hemdal]

Sorry, i dont know.
Maybe @Jay Hemdal can help.

That isn’t acutely toxic to fish, but they may show poor color, etc. The trouble is that tanks with really high phosphorus also have other issues including high nitrate, lower pH, things like that. Generally, it is “old tank syndrome” - a combination of those factors that cause chronic fish health issues.

 

[CHSUB]

a combination of those factors that cause chronic fish health issues.

I find this comment interesting, maybe only in terms of confirmation bias? When someone brags, “ high nutrients are fine, look at me”, do we really know the long term health effects of elevated no3 on fish health? Maybe after a few years the fish develop cancer and tumor, we are encouraged to avoid nitrates in our own diet and our fish’s nature environment is nutrient poor. Should we not strive to maintain a similar environment in our glass boxes?

 

[Jay Hemdal]

I find this comment interesting, maybe only in terms of confirmation bias? When someone brags, “ high nutrients are fine, look at me”, do we really know the long term health effects of elevated no3 on fish health? Maybe after a few years the fish develop cancer and tumor, we are encouraged to avoid nitrates in our own diet and our fish’s nature environment is nutrient poor. Should we not strive to maintain a similar environment in our glass boxes?

There is some history behind this - in the 1970's through the 1980's, it was pretty typical for public aquariums to have nitrate levels > 100 ppm and the fish did fine for decades (I cared for a tarpon for a few years that lived in such water from 1935 until 1998). Then, with the advent of reef aquariums, the nitrate (and other compounds) needed to be more tightly controlled for the health of the corals. Even with new life support systems, public aquarium fish-only exhibits have nitrate levels that run from 20 to 60 mg/l

 

[CHSUB]

There is some history behind this - in the 1970's through the 1980's, it was pretty typical for public aquariums to have nitrate levels > 100 ppm and the fish did fine for decades (I cared for a tarpon for a few years that lived in such water from 1935 until 1998). Then, with the advent of reef aquariums, the nitrate (and other compounds) needed to be more tightly controlled for the health of the corals. Even with new life support systems, public aquarium fish-only exhibits have nitrate levels that run from 20 to 60 mg/l

Thanks for your insight. I’m a low “nutrient guy”, so whenever I see something that even marginally supports my belief, I jump….haha!