PO4 in my RO/DI water with 0 TDS

Tank Facts · Jun 7, 2019

I know a TDS meter does not measure phosphate.

So I have been battling a type of hair algae in a tank for some time now. The common species that eat algae (tangs, sea hares, etc...) do not touch the stuff. I have been melting it away with hydrogen peroxide and afterward doing a significant water change to remove some of the organics released into the water. Water changes only seem to make the algae grow quicker.

My API test seems to show everything fairly much inline PO4 for the tank <.05 and freshly mixed saltwater at 0.00.

After months of dealing with it, I decided to do an ICP test on my Aquarium, Freshly Mixed Saltwater, and my RO/DI water.

I seem to have an issue with Phosphates and Phosphorus, kind of what I figured to start with. But interesting enough my 0 TDS water that the filters and changed religiously seems to be the source of the Phosphates.

Aquarium
- P = 37
- PO4 = 0.11322

Freshly Mixed Saltwater
- P = 6.862
- PO4 = 0.02099

RO/DI
- P = 64
- PO4 = 0.19584

Surprisingly, the lowest reading came from the freshly mixed saltwater (Fritz Pro) I am not sure if they add something to their salt to reduce PO4.

So the source of the issue seems to be the RO/DI water, my inline TDS reads 0 and my handheld TDS meter reads 0.

I am not sure how to deal with the issue.
- Adding GFO to the aquarium does not make sense how the source of the problem is not coming from the aquarium (overfeeding, maintenance, etc...)

- I do not know of a filter that I can add to remove PO4 from my RO/DI unit

- I could rig a GFO reactor to my RO/DI mixing station and have it strip out the PO4 there before its used for saltwater or for topping off my tank, but this seems like a pain.

Did anyone out there have a similar issue?

I found a post from someone who had the same issue, but the post was from 2015, I sent the person a message, but they have not logged on to R2R in over two years. The post had some discussion about what it could be, but nothing was ever defined as a solution.

Several years ago I swapped out my RO / DI unit from a BRS to the Aquatic Life twist unit to make replacing the filters quicker and easier. I do not know if I had the same issue with the BRS RO / DI unit as well and did not know my guess is that I did how they were both 4 stage filters.

ideas, thoughts, comments?

Big G · Jun 7, 2019

Tank Facts · Jun 7, 2019

Also just FYI, on a different forum people insisted that the ICP test must be wrong how the mixed saltwater had such lower PO4 reading.

I tested the RO/DI water with my API test kit and the RO/DI shows a higher level of PO4 then the Freshly Mixed Saltwater using the same RO/DI water.

The ICP test is an ICP Triton test in case anyone wanted to know who did the ICP test.

Keesers · Jun 7, 2019

Tank Facts said:
I know a TDS meter does not measure phosphate.

So I have been battling a type of hair algae in a tank for some time now. The common species that eat algae (tangs, sea hares, etc...) do not touch the stuff. I have been melting it away with hydrogen peroxide and afterward doing a significant water change to remove some of the organics released into the water. Water changes only seem to make the algae grow quicker.

My API test seems to show everything fairly much inline PO4 for the tank <.05 and freshly mixed saltwater at 0.00.

After months of dealing with it, I decided to do an ICP test on my Aquarium, Freshly Mixed Saltwater, and my RO/DI water.

I seem to have an issue with Phosphates and Phosphorus, kind of what I figured to start with. But interesting enough my 0 TDS water that the filters and changed religiously seems to be the source of the Phosphates.

Aquarium
- P = 37
- PO4 = 0.11322

Freshly Mixed Saltwater
- P = 6.862
- PO4 = 0.02099

RO/DI
- P = 64
- PO4 = 0.19584

Surprisingly, the lowest reading came from the freshly mixed saltwater (Fritz Pro) I am not sure if they add something to their salt to reduce PO4.

So the source of the issue seems to be the RO/DI water, my inline TDS reads 0 and my handheld TDS meter reads 0.

I am not sure how to deal with the issue.
- Adding GFO to the aquarium does not make sense how the source of the problem is not coming from the aquarium (overfeeding, maintenance, etc...)

- I do not know of a filter that I can add to remove PO4 from my RO/DI unit

- I could rig a GFO reactor to my RO/DI mixing station and have it strip out the PO4 there before its used for saltwater or for topping off my tank, but this seems like a pain.

Did anyone out there have a similar issue?

I found a post from someone who had the same issue, but the post was from 2015, I sent the person a message, but they have not logged on to R2R in over two years. The post had some discussion about what it could be, but nothing was ever defined as a solution.

Several years ago I swapped out my RO / DI unit from a BRS to the Aquatic Life twist unit to make replacing the filters quicker and easier. I do not know if I had the same issue with the BRS RO / DI unit as well and did not know my guess is that I did how they were both 4 stage filters.

ideas, thoughts, comments?

Yeah bud no problem with GFO reactor on RODI took two seconds and cost ten dollars plus media. It’s the last stage before it dumps in my bucket. Not sure if it’s social “reef acceptable” or not but works great for me. Took it from .25 to 0 I thought there was a problem on main tank cause I was adding phosphate in with my top off water and saltwater problem solved.

Tank Facts · Jun 7, 2019

So you added a GFO reactor after your RO/DI unit. I was thinking of circulating water into the GFO reactor on my RO/DI storage unit. So you stopped it before it even got to the storage unit. Interesting I thought it would have to pass through the GFO a few time before it removed all of the phosphates that is why I was thinking about attaching the reactor to the storage unit vs the RO/DI unit.

Keesers · Jun 7, 2019

Tank Facts said:
So you added a GFO reactor after your RO/DI unit. I was thinking of circulating water into the GFO reactor on my RO/DI storage unit. So you stopped it before it even got to the storage unit. Interesting I thought it would have to pass through the GFO a few time before it removed all of the phosphates that is why I was thinking about attaching the reactor to the storage unit vs the RO/DI unit.

Yeah it runs though it slow enough though the top and out the bottom It may not work same for every situation. I make my water Proly slower then some. And I completely agree a reactor in the storage bin would probably get more turn over rate and pull it out even more if the water was higher then mine. I totally didn’t even think of that I Suppose it depends how high the phosphate is which method would work best maybe a bag of media in there with your circulation pump may just do the trick but more of a pain in the butt I think having to do the bag. Never tested the water after salt was added test mine before. Best of luck let us know what you end up doing.