Rebooting a tank with Off the chart phosphate. Help!

[Spartan76]

A brief summary- The system is about 285g of water volume (180 g display, 55g fuge, 100g sump). The tank was set up in 2003. Had sps with good success for 5-6 years. My circumstances changed and couldn’t keep up with the sps regimen. So it then was a softie tank for about a decade with a very high bioload. Last couple of years has been FO with just a couple softies. I did very few water changes over the past couple years.
Now I want to return to sps but I need to keep as low a maintenance time commitment as possible. Testing for phosphate and nitrates was off the charts a few months ago - not a surprise. I took out all of my sand, all corals but 2 small softies and a RBTA and went bare bottom. Cut the fish load by about 50% by mass, although perhaps it may still be on the high side (currently 3 tangs avg size 4”, 2 small clowns, 2 wrasses 3”, flame hawk 3”, and 1 angelfish 8”. Put in roller mat. Stocked the refuge with three softball size chaeto clumps and a fist size clump of caulerpa. The chaeto has not grown much, while the caulerpa has about doubled. And started doing water changes of course. Over the last month 40g water change per week. Started a carbon reactor and GFO last week. I started a bit lower than the recommended dose and used 10 tbsp.
Sent ICP test prior to the above : PO4 = 1.879 ppm. Yikes! Now 1.411 ppm, better but still insanely high.
I’ve sent out nitrate test to the lab also, and I expect that will be extremely high as well.
Where to go from here? I don’t think water changes are going to be enough - the live rock might have a lot of retained phosphate over the years? Throwing out the rock is something I would not want to do as I suspect that would destroy my biome and I like my aquascape.
I used on online calculator that said I’d need 1500 ml (or 102 tbsp) of RowaPhos to go from 1.411 to 0.02ppm. Obviously that can’t be done in one dose.
I’ve never heard of levels this high and this is just the PO4. There’s no way I can start sps until I’m back in the safe range.
Please advise -—max safe dose of GFO or RowaPhos ? How often to change that out in this situation? Weekly?
Start nopox ? Microbacter 7? Other?

 

[DanyL]

That's a good case for considering the use of Lanthanum.

If you can treat the rocks outside of the system, that'll be best.

Otherwise, you'll need to go super slow because it is known to cause issues with both tangs and wrasses if not used carefully. In this case, take an IV bag and fill it with diluted lanthanum (I wouldn't recommend more than a 0.2-0.3 drop every 3 days) and set it off with 1 drop per ~5 seconds into a 5 micron sock with running water.

Before using Lanthanum you must read more about it, do your homework because it is quite dangerous if not used with care.

 

[Spartan76]

I’m really not comfortable with Lanthanum which I‘ll save as a last resort. Maybe just ramp up the GFO?
may be no pox too? Other ideas???
NDoc test still pending….

 

[DanyL]

With all honesty, Lanthanum really is the most logical path to go with here.
Otherwise you'll run through a lot of GFO, more than you're willing to pay for, believe me.
It won't end with the nice 1.5kg of GFO the calculator suggested, because it was also accumulated inside your rock work and will start leaching it back to the water column as you pull it out, that's at least what I experienced when my live rock finally reached its full capacity after more than a decade.

nopox (or any other carbon source) will grow bacteria and it can be pulled later on with your skimmer.
But for the amount of phosphates you have you'll need to dose nitrates at some point and more than likely to experience a bacterial bloom.

It won't be very quick with Lanthanum either, because you'll have to do this slowly, spread over multiple small doses, but you should be able to get to your target within 2 to 3 weeks using it alone, add regular large water changes which you'll have to do regardless and you should be fine rather quickly compared to other methods.

Just to assure you that if it's done correctly it can be safe, I used it to take my PO4 from 0.18 to around ~0.05 within a few days and that's in a 206g tank with 7 tangs, 4 wrasses around 10 more fish and hundreds of corals (most of which are SPS, lots of acros) and some are 15 years in my possession (both corals and fish). It went without any ill effects.
Again - I went slowly, used an IV bag and a 5 micron sock. Thats the key to ensure it doesn't shock your fish.

 

[Randy Holmes-Farley]

I’m really not comfortable with Lanthanum which I‘ll save as a last resort. Maybe just ramp up the GFO?
may be no pox too? Other ideas???
NDoc test still pending….

Yes to GFO, no to NOPOX or any other type of organic carbon dosing. It wills trip nitrate and leave you with excess phosphate.

 

[chipmunkofdoom2]

Agreed on lanthanum chloride.

The PO4 isn't just in your water. If you did a 100% water change with new saltwater with zero phosphates, chances are the PO4 would rise back up to about where it is now. The problem is that aragonite surfaces adsorb PO4. So you don't just need to account for the PO4 in your water, you also need to account for all the PO4 that's been building up on your rock's surface. And that's a really hard number to calculate.

If you're concerned about your livestock, you could treat individual rocks outside the display.