Ideas on quick phosphate control
 

So let's say you had a 300g tank that you transferred an existing 300g full of SPS into in one day. Then let's say you tested PO4 and found it to be close to 3PPM.

How would you manage that? I have no experience with phosphate issues and I'm not sure how to help this guy. Ideas?

100 % water change?

Ya, suggested that. But that's a lot of water to make and store and move. Also suggested fozdown.

Problem is the rock is all old dead rock that will keep leaching, so that would be multiple 100% changes over a few months.

What was the po4 level at normally in the old 300?

phosphate
 

use precision solutions phosphate reducer-more bang for your buck,10-15 gal waterchange every 1-2 days(as not to shock the system) add a bag of seachem roaphos(if i remember right) and change out every three days.keep monitoring every 2-3 days till you can cut back on the waterchanges and seachem.keep using phosphate reducer (about 180 drops a day-i was using 160 in my 240).run roaphos to keep it stable

I'm guessing the same. He had 21 tangs in it :(

Lanthium chloride. Dose according to bottle and test your ALK.

Yes lanthium chloride works wonders for removing PO4 quickly, just be carerfull

Actually a 100% water change will do very little as the phosphate is bound to other thing in the tank , the good news is phosphates have a limit so it can only leach so long.

I agree lanthum chloride will do it but won't happen over night and the amount you'll need is going to be expensive .

Personally I'd set up a temp frag tank with good water while I dealt with the 300g ,I would get water bak n track as I'm sure if it's truly 3ppm then there's probably other issues as well.

I can assume you've double checked the testers