Phosphates in new saltwater

[Miami Reef]

I just tested my TDS in my RO/DI water, and it’s showing 0-1ppm (the inline TDS shows 0ppm)

I made saltwater (35ppt) and added 18g of sodium bisulfate to lower the alkalinity to around 7dKH.

I tested the water only a few hours after adding the acid. In my initial test, I rinsed the beaker inside the clean saltwater to ensure no residue could skew the results. I rinsed all my vials and syringes a few times with salt water. I collected my first sample of water in a beaker.

The phosphates from the beaker were 0.12ppm.

I took the second test sample directly from the brute trash can (I only put clean saltwater inside), and it tested 0.16ppm, which was higher than the beaker.

I am using Hanna ULR PO4.

Are the phosphates coming from the RO/DI, the salt (instant ocean purple,) the sodium bisulfate, or somewhere else?

I want to believe it’s coming from my RO/DI, but I tested my water after the membrane (ICP around 6ppm), and there weren‘t any phosphates in that ICP. The ICP (ATI) tests freshwater separately from saltwater.

 

[lapin]

I just tested my TDS in my RO/DI water, and it’s showing 0-1ppm (the inline TDS shows 0ppm)

I made saltwater (35ppt) and added 18g of sodium bisulfate to lower the alkalinity to around 7dKH.

Did you test the container water before adding salt and sodium bisulfate ?

I tested the water only a few hours after adding the acid. In my initial test, I rinsed the beaker inside the clean saltwater to ensure no residue could skew the results. I rinsed all my vials and syringes a few times with salt water. I collected my first sample of water in a beaker.

The phosphates from the beaker were 0.12ppm.

I took the second test sample directly from the brute trash can (I only put clean saltwater inside), and it tested 0.16ppm, which was higher than the beaker

 

[Miami Reef]

Did you test the container water before adding salt and sodium bisulfate ?

Will the hannah phosphate checker work on freshwater?

 

[Sean Clark]

This is right on the edge of Hanna's accuracy statement of ±0.04 ppm ±4% of reading.

I wouldn't sweat it.

Edit: that is for the phosphate checker (HI713).

Are you using the ulr phosphate checker (HI774) which is still close at ±0.02 ppm ±5% of reading.

 

[Miami Reef]

This is right on the edge of Hanna's accuracy statement of ±0.04 ppm ±4% of reading.

I wouldn't sweat it.

My checker (Hannah phosphate ULR has an accuracy of ±0.02 ppm ±5% of reading

But besides for that, my new saltwater mix needs to be 0.00ppm. Anything above that is too much for new saltwater, at least for me.

 

[Miami Reef]

@Randy Holmes-Farley

I put most of the sodium bisulfate in the water before adding any of the salt.

I put 15g and I tweaked the alkalinity level by testing. So I added 3 more grams after the salt was already mixed in.

Do you think the plain acid in freshwater caused this phosphate? Maybe the acid dissolved some of the brute can which released something? Or maybe it was my pump that got “dissolved”

I don’t know what’s causing this.

 

[Garf]

@Randy Holmes-Farley

I put most of the sodium bisulfate in the water before adding any of the salt.

I put 15g and I tweaked the alkalinity level by testing. So I added 3 more grams after the salt was already mixed in.

Do you think the plain acid in freshwater caused this phosphate? Maybe the acid dissolved some of the brute can which released something? Or maybe it was my pump that got “dissolved”

I don’t know what’s causing this.

I’d probably mix a bit of salt in a glass with your RODI and test that, see what shows, eliminate the bisulfate and brute can in one fair swoop.

 

[Miami Reef]

I’d probably mix a bit of salt in a glass with your RODI and test that, see what shows, eliminate the bisulfate and brute can in one fair swoop.

Well, I just changed my DI resin. It was about to get exhausted anyway.

I will make a batch soon. I think I’ll do it either tonight or tomorrow. Depends on how I feel haha.

 

[Miami Reef]

Update. Nitrates are 0ppm in the brute (The one in the OP that gave 0.12-0.16ppm PO4)

 

[iaa12]

Can you just add some Phosphat-E to the Brute trash can and call it a day.

 

[rtparty]

Not saying it came from the salt but I wouldn’t be surprised in the least if it did. I wouldn’t hesitate to use it. Corals love a little phosphate.

Then I’d figure out why I’d use a salt that has parameters that far off from what I want to run. So many good salt choices out there that you can find multiple that need zero tweaking beforehand

 

[kados]

15 years in saltwater aquariums and I swear I understand half of what I read around here. I made the switch to FOWLR and never looked back. More power to all the chemists on here. And trust me, I mean that with respect. Everything sounds more complicated than it needs to be in reefing.

 

[Miami Reef]

I made 35ppt saltwater using pure 0ppm water and IO Salt.

It‘s in the checker. 1 minute and 34 seconds Remaining

Be patient please! Let’s hold our horses.

 

[Miami Reef]

Bingo. 0.00ppm phosphates.

So the issue was either the RO/DI (I corrected that), the brute, or the acid.

I’m gonna use some GFO to bring the bucket to 0ppm.

I think this will solve the issue for the future.

Thanks! Ps, I like experimenting and understanding why things are the way they are. If I didn’t like it, I wouldn’t do it.

 

[Randy Holmes-Farley Verified Community Expert]

It is not uncommon to see some phosphate and silicate in Ro/DI water, especially if it is close to depletion.

Could it have been from other sources? Yes, but it is not typical to see significant phosphate in IO.

It would be interesting to see if it was the acid.

 

[Miami Reef]

I made new saltwater, and I tested it before and after the acid.

It was definitely the RO/DI that added the phosphates.

 

[EeyoreIsMySpiritAnimal]

@tehmadreefer , what's so funny??

 

[Randy Holmes-Farley Verified Community Expert]

I made new saltwater, and I tested it before and after the acid.

It was definitely the RO/DI that added the phosphates.

Good to know. Thx!