Phosphate conundrum... Where is it coming from?

[Reefin' Alaska]

I haven't tested my tank in a while as everything seemingly was going well. Some brownish algae showed up on the sand, and it seems to go away at night. My thought was Dino's so I tested the display. Nitrates came back as 5.2.. However, phosphate.

Came back as 171ppb on the Phosphorus ULR tester, and .59 on the H736 tester.

Tested my saltwater vat, at .33.. I'm using the Red Sea salt, blue bucket.

Using the H713 which "says" it works in freshwater, I get .04. Testing error range is -/+ .04 on that tester. Not sure if I can even consider that useful.

RO/DI filters changed in Jan. The DOW membrane is going on 3 1/2 years old, that wasn't changed because the end was cracked when I got it. BRS replaced it, I just never installed it.

Ruling out the RO/DI, I would assume it's the salt, or the vat it sits in. Not really even sure where to start?

 

[Miami Reef]

What is the TDS coming out of the Di? Once the Di is exhausted the PO4 can escape elevated.

I don’t think the salt is the reason for the PO4 readings.

In any case, the phosphates added from the water change isn’t that important. We add significantly much more PO4 from the daily feedings than high PO4 top off/water changes can add.

I don’t think lowering phosphates will solve the brown algae. I think it’s likely the Di is exhausted and might be adding silica (perhaps the algae is diatoms) and maybe even some PO4.

You need to microscope the algae to be sure it isn’t dinos. Leaving at night is a sign of them. In rare cases, dinos can flourish in higher nutrient tanks.

 

[Reefin' Alaska]

What is the TDS coming out of the Di? Once the Di is exhausted the PO4 can escape elevated.

I don’t think the salt is the reason for the PO4 readings.

In any case, the phosphates added from the water change isn’t that important. We add significantly much more PO4 from the daily feedings than high PO4 top off/water changes can add.

I don’t think lowering phosphates will solve the brown algae. I think it’s likely the Di is exhausted and might be adding silica (perhaps the algae is diatoms) and maybe even some PO4.

You need to microscope the algae to be sure it isn’t dinos. Leaving at night is a sign of them. In rare cases, dinos can flourish in higher nutrient tanks.

The resin is still black. The TDS on the meter on the RO/DI unit itself is 0 in and out. The TDS meter reading in the RO/DI reservoir is also 0.

Resin isn't but 4-5 months old.

It wasn't specifically the brown algae I was concerned with, it's just what urged me into testing. I did lose a frag of Acro earlier this month. I had just went back to work after my daughter was born, and I didn't test then. In hindsight, I probably should have.

 

[Reefin' Alaska]

To add, I did just take 5 gallons of water and mixed a fresh batch of saltwater in a 5 gallon bucket. I will test that here shortly.

 

[Miami Reef]

I really don’t think phosphates 0.59ppm will cause acro death.

You can definitely try to fix the phosphate though.

If Di is still unchanged and TDS is 0, then I agree that the source water isn’t the cause for the PO4.

Let us know what the PO4 tests in the new bucket.

 

[Miami Reef]

I had just went back to work after my daughter was born

Congratulations.

 

[VintageReefer]

How is your tds measuring 0 on the input before rodi filtration? That makes me think the tds meter isn’t lined up correctly or is defective

 

[Miami Reef]

How is your tds measuring 0 on the input before rodi filtration? That makes me think the tds meter isn’t lined up correctly or is defective

Good point. I didn’t even realize that.

 

[Reefin' Alaska]

Good point. I didn’t even realize that.

Alaska water is quite good already.

To add to that, I don't use the TDS meter on the unit, I only did in this case just as something to compare it with. I have 2 other TDS meters I use.

 

[Reefin' Alaska]

Congratulations.

Thank ya. =)

 

[Reefin' Alaska]

How is your tds measuring 0 on the input before rodi filtration? That makes me think the tds meter isn’t lined up correctly or is defective

I rarely use the TDS meter on the unit itself. I only did this time as a comparison.

"In" on the RO/DI unit is after the RO membrane. Alaska water is already good, and you could likely get away without DI resin altogether, depending on where you live.

I can go about 18 months before my DI resin starts to change color.

I have 2 other TDS meters.

 

[Miami Reef]

Alaska water is quite good already.

To add to that, I don't use the TDS meter on the unit, I only did in this case just as something to compare it with. I have 2 other TDS meters I use.

Thank you for clarifying. Did you get the phosphate results from the 5 gallon bucket yet?

 

[Randy Holmes-Farley]

Alaska water is quite good already.

To add to that, I don't use the TDS meter on the unit, I only did in this case just as something to compare it with. I have 2 other TDS meters I use.

Maybe, but there is no natural tap or well water that is 0 ppm tds.

 

[Reefin' Alaska]

Maybe, but there is no natural tap or well water that is 0 ppm tds.

It's 0 after the RO membrane if you use the TDS meter on the unit itself.

I also used an HM TDS meter on the RO reservoir and it was also 0.

 

[Reefin' Alaska]

Thank you for clarifying. Did you get the phosphate results from the 5 gallon bucket yet?

I did.. bucket tested .03 ..

I did do an ICP just because I'm wondering if the samples became contaminated somehow with the syringe I used to take water from tank. I can't figure anything else, because the sample that tested .59 became very visably blue after adding the reagent, and that's never happened before, and it happened on both the HI736 and the Phosphorus testers.

 

[Miami Reef]

I did.. bucket tested .03

That’s what it should test. Try using a new syringe.

One time a reefer used a syringe they dosed phosphate with, and their tank’s PO4 showed extremely high. They kept overdosing lanthanum and testing with the contaminated syringe…turned out their tank was undetectable the entire time.

If the 5 gallon bucket showed low PO4, then you can rest assured knowing that the salt and the water is not the problem.

 

[Dan_P]

The resin is still black. The TDS on the meter on the RO/DI unit itself is 0 in and out. The TDS meter reading in the RO/DI reservoir is also 0.

Resin isn't but 4-5 months old.

It wasn't specifically the brown algae I was concerned with, it's just what urged me into testing. I did lose a frag of Acro earlier this month. I had just went back to work after my daughter was born, and I didn't test then. In hindsight, I probably should have.

Mix up a small amount of new saltwater and test (make sure the solution is clear, no haze). Let’s confirm the observation 0.33 ppm.

 

[Randy Holmes-Farley]

It's 0 after the RO membrane if you use the TDS meter on the unit itself.

I also used an HM TDS meter on the RO reservoir and it was also 0.

Ok, that’s plausible, but if you are using anchorage public water, I don’t think it is entirely accurate. The water company reports tds from 110 to 290 ppm, which would not typically be 0 ppm tds post ro.

https://www.awwu.biz/home/showpublisheddocument/2288/638430637220630000

 

[Reefin' Alaska]

Ok, that’s plausible, but if you are using anchorage public water, I don’t think it is entirely accurate. The water company reports tds from 110 to 290 ppm, which would not typically be 0 ppm tds post ro.

https://www.awwu.biz/home/showpublisheddocument/2288/638430637220630000

My water in the Potter Valley area has tested between 40-80 since 2021. The only time we ever saw above 80 was right after the 2018 7.1 earthquake when for a period of time it was over 600.

 

[907_Reefer]

Sounds like the tank has been running for a while? Any changes in feeding, or otherwise in the tank?

I'm not a good comparison, but about an hour north in the valley here we are 211 TDS from the tap on my last test, 0-1 after 4 stage RODI. Using live rock from our LFS and I feed heavy, always .6 to .9 PO4... 55g with ~85 lbs rock, moved the tank twice, always had high PO4. Red Sea Coral Pro / black bucket.

Free bump anyway lol..