Stubbornly high Phosphate

[carri10]

Hello all.

For months (like 6 months) I have had PO4 at around 0.3ppm. I have never freaked out about this, because it is the prevailing thought seems to be this is high, but not dangerously so.
Over the last 4 months, however, I decided to try some Rowaphos to bring it down to nearer 0.1ppm.

I now use 300ml of Rowaphos (after experimenting with ramping up) changed every two weeks in a 1250l (330gallon) tank and phosphate DOES NOT MOVE. I test every weekend, same time and despite these (very) large amounts of rowa in a rector, it will not go down.
I have read about bound phosphate in rocks releasing back into the ater column once below the equilibrium point, but can I really have sp much bound phosphate that it taks several months of this large amount of Rowa to remove?

Any ideas or experience out there?

 

[Randy Holmes-Farley]

That value matches mine and I’m perfectly happy with it. I personally would do nothing. Some great tanks have far higher phosphate.

There are many fine ways to reduce phosphate, but all of them have drawbacks of one sort or another.

 

[carri10]

Thanks. Yep, I wasn’t too panicked about it at all, but what does confuse me is the massive application of Rowaphos has not had any effect on the phosphate level. I’m using Hannah ULR as my tester by the way.

 

[Randy Holmes-Farley]

It can take a lot of GFO for a long while to offset both the ongoing food additions and to try to strip what is bound to rock and sand., some folks resort to lanthanum for that reason.

 

[carri10]

Okay. I’ll not worry about it then.

 

[Alexander1312]

Agreed, it takes quite a while due to where it is stored and keeps releasing it when you remove it from the water column.

I had the same levels, and goals, you can see in the chart below.

I added weekly (!) the maximum recommended GFO amount with very little effect for months until it came down more or less suddenly, without changing feeding or anything else.

The weekly replacement/addition is key in my opinion, but can get expensive if it takes long.

In my case, I did not remove the gfo and replace it every but added weekly the new gfo onto the existing gfo until the reactor was full, and then replaced everything in the reactor.

 

[carri10]

Thanks for the experience. Glad to learn from you.

 

[Bear22]

Questions for the chemistry gurus: Does lanthanum chloride make PO4 "unusable" for hard corals?

 

[Bear22]

Questions for the chemistry gurus: Does lanthanum chloride make PO4 "unusable" for hard corals?

 

[carri10]

Yes. It precipitates it out of solution. It is no longer available to anything in the water.

 

[Bear22]

Yes. It precipitates it out of solution. It is no longer available to anything in the water.

Can you provide some analysis/findings in written form of this?

 

[Randy Holmes-Farley]

Can you provide some analysis/findings in written form of this?

Not sure what you are asking. Phosphate needs to get to an organism for it to use it. If it is sitting as a solid precipitate it is unusable. Most folks try to remove the precipitate with a skimmer or mechanical filter.

If you are asking if there may be scenarios where solid
Lanthanum phosphate can redissolve, then yes there are, but it would typically involve either lanthanum or phosphate or
Both dropping to very low levels, or very low
pH.

It is a natural process. Lanthanum phosphate precipitates in the deep ocean, and that is believed to limit the lanthanum concentration in the ocean.