I'm just going to think out loud here and do the back-of-the-envelope math. Monosodium phosphate has a density of 2.36 g/cm^3. Eight tablespoons is appx. 120 cm^3. Now, I know that there is some air between the particles, so let's estimate 10% air, so that's 120 * 2.36 * 0.9 = 254 -- let's call it 250 grams that you dumped in. Monosodium phosphate is around 79% PO4 (let's call it 80%), so that's 250 * 0.8 = 200 grams of PO4 in your 225 gallons. 225 gallons is around 850 liters, so that's 200 / 850 = 0.235 grams per liter, which = 235 mg/L = 235 PPM. Ouch! I hope I've made some mistake here, and if I have, somebody please point it out, but I don't think I have.

You could get the hanna lr, 0 to 2.5ppm. $50 for a data point.
Hopefully you are on that scale.
Keep at the lc, the rocks and sand are still loaded.
Into a 5 micron sock for sure.

If my math is right, and I have a pretty good track record that way, there may even be enough adhered to the glass surface to be a problem even if you chucked all the rock, sand, and water, and started over with an empty tank.

200+ PPM is an awful lot. Phosphate is really "sticky".

Again, I'm sincerely hoping I made a mistake somewhere.

I'm just going to think out loud here and do the back-of-the-envelope math. Monosodium phosphate has a density of 2.36 g/cm^3. Eight tablespoons is appx. 120 cm^3. Now, I know that there is some air between the particles, so let's estimate 10% air, so that's 120 * 2.36 * 0.9 = 254 -- let's call it 250 grams that you dumped in. Monosodium phosphate is around 79% PO4 (let's call it 80%), so that's 250 * 0.8 = 200 grams of PO4 in your 225 gallons. 225 gallons is around 850 liters, so that's 200 / 850 = 0.235 grams per liter, which = 235 mg/L = 235 PPM. Ouch! I hope I've made some mistake here, and if I have, somebody please point it out, but I don't think I have.

If this is correct, you could do a 99% water change and your phosphate could still be over 2.35 PPM. And that is assuming that none of the phosphates were absorbed by the sand and rocks and released into the new water.

So I would dose heavily with the Lanthanum chloride and then removed the precipitates via significant water change. Maybe 75%+. I have have 75%+ water changes with no impacts before as long as the parameters other than phosphate matches.

everything is alive , even the LPS are thriving ( the one frogspawn frag i have ) and all 20 fishes. Thanks to all, ill keep dripping the LC into filter socks , today i am boosting the LC to 30ml a day... eventually it will be back to 0.05

So, if I go thru all 32 ounces of seaklear phosphate remover dosing 30mls a day and still have .9ppm on the phosphates- after all that, if I remove all the water at once doing a 100% water change and start back up with new real reef rock- or take all the old rock out now and change like 50% of the water and then add in the new real reef rock, can this work or will the acrylic tank be ruined forever by the phosphate?

I'm just going to think out loud here and do the back-of-the-envelope math. Monosodium phosphate has a density of 2.36 g/cm^3. Eight tablespoons is appx. 120 cm^3. Now, I know that there is some air between the particles, so let's estimate 10% air, so that's 120 * 2.36 * 0.9 = 254 -- let's call it 250 grams that you dumped in. Monosodium phosphate is around 79% PO4 (let's call it 80%), so that's 250 * 0.8 = 200 grams of PO4 in your 225 gallons. 225 gallons is around 850 liters, so that's 200 / 850 = 0.235 grams per liter, which = 235 mg/L = 235 PPM. Ouch! I hope I've made some mistake here, and if I have, somebody please point it out, but I don't think I have.

so Randy, if I go thru all 32 ounces of seaklear phosphate remover dosing 30mls a day and still have .9ppm on the phosphates- after all that, if I remove all the water at once doing a 100% water change and start back up with new real reef rock- or take all the old rock out now and change like 50% of the water and then add in the new real reef rock, can this work or will the acrylic tank be ruined forever by the phosphate?

so Randy, if I go thru all 32 ounces of seaklear phosphate remover dosing 30mls a day and still have .9ppm on the phosphates- after all that, if I remove all the water at once doing a 100% water change and start back up with new real reef rock- or take all the old rock out now and change like 50% of the water and then add in the new real reef rock, can this work or will the acrylic tank be ruined forever by the phosphate?

The acrylic tank is not ruined. It may need to have precipitate cleaned from it, if it is clouded with solids.

I'm not sure how much phosphate to expect to still be in the water as a lot likely precipitated as magnesium and calcium phosphate, independent of the Seakler additions.

The acrylic tank is not ruined. It may need to have precipitate cleaned from it, if it is clouded with solids.

I'm not sure how much phosphate to expect to still be in the water as a lot likely precipitated as magnesium and calcium phosphate, independent of the Seakler additions.

ok, ill just keep dripping 30mls a day of seaklear into the tank until i see some lowering in the phospahtes... either way the rock needs to be replaced im afraid.