phosphate testing question

landlubber · Jul 5, 2017

i have been trying to keep phosphate at 0.04ppm nitrates between 2ppm-5ppm with regular feeding, nutrient export and water changes. while i'm having success with my nitrates sitting stable i find that my phosphates vary greatly over the course of the day and it got me thinking, while i know the idea is to test at the same time each test to get my numbers what truly makes for a 0.04ppm phosphate test? realistically my average phosphate level would probably be closer to 0.12ppm considering i've seen it as high as 0.20ppm immediately after feeding at night down to my desired 0.04ppm when it's been 10 hours since feeding the tank.

saltyfilmfolks · Jul 5, 2017

Following along. But I don't believe Po4 will vary that greatly in general over the course of hours or days.

What test your using may help explain the situation.

HolisticBear · Jul 5, 2017

landlubber said:
i have been trying to keep phosphate at 0.04ppm nitrates between 2ppm-5ppm with regular feeding, nutrient export and water changes. while i'm having success with my nitrates sitting stable i find that my phosphates vary greatly over the course of the day and it got me thinking, while i know the idea is to test at the same time each test to get my numbers what truly makes for a 0.04ppm phosphate test? realistically my average phosphate level would probably be closer to 0.12ppm considering i've seen it as high as 0.20ppm immediately after feeding at night down to my desired 0.04ppm when it's been 10 hours since feeding the tank.

I don't have the number handy, but Randy has mentioned a few times how much P04 a single feeding can add.

To get consistent P04, I like to test in the morning before my first feeding. This is probably it's lowest, but testing following a big feeding might be temporary skewed. Also, PO4 media can be exhausted quick. The label on Phosguard says it can be exhausted in four days, so if testing days vary when you replace media that can be a factor.

HolisticBear · Jul 5, 2017

MrMichael said:
I don't have the number handy, but Randy has mentioned a few times how much P04 a single feeding can add

Typical phosphate coming from foods is about 0.02 to 0.3 ppm per day. So consumption can easily be roughly that same amount.

Found Randy's post, so if food can add 0.3 and you're trying to maintain 0.04 (1/7 what food can add), then it seems you need to test when food isn't a factor. If you happen to be using food that only adds 0.02 then testing time is less important, but if your foods add 0.3ppm .....

Randy Holmes-Farley · Jul 6, 2017

FWIW, it isn't clear to me how fast the consumed phosphate would be released, but certainly it gets spread over time. In a person it would be excreted over hours. mostly, and some longer. Reef tank creatures probably digest a lot faster, but it will still take time.

I wouldn't worry much about changes over time unless you have an algae problem.

saltyfilmfolks · Jul 6, 2017

Randy Holmes-Farley said:
FWIW, it isn't clear to me how fast the consumed phosphate would be released, but certainly it gets spread over time. In a person it would be excreted over hours. mostly, and some longer. Reef tank creatures probably digest a lot faster, but it will still take time.

I wouldn't worry much about changes over time unless you have an algae problem.

I theory phosphate from a food should not be detectable correct? A shrimp as an example.

Unless an additive is used for freshness or preservative. As I understand it this is actually not the case and phosphate is not used in this way.

Randy Holmes-Farley · Jul 6, 2017

Phosphate from a shrimp (in the form of its organic tissues such as DNA, RNA, phospholipids, phosphorylated proteins, etc.) isn't detectable by ordinary kits until the food is digested and inorganic phosphate is released. Then most of it is released to the water and is detectable.

saltyfilmfolks · Jul 6, 2017

Randy Holmes-Farley said:
Phosphate from a shrimp (in the form of its organic tissues such as DNA, RNA, phospholipids, phosphorylated proteins, etc.) isn't detectable by ordinary kits until the food is digested and inorganic phosphate is released. Then most of it is released to the water and is detectable.

Thank you. As I thought.
That kills internet rumor.
Again.

HolisticBear · Jul 6, 2017

saltyfilmfolks said:
I theory phosphate from a food should not be detectable correct? A shrimp as an example

If your food was one of the phytoplankton in a bottle or one of the many frozen reef foods, it could be, yes?

At least in the sense of increasing a 0.04 reading to 0.08 especially in a smaller body of water?? Obsessing about number may be the larger issue, but I'm sure many people obsess between those two different values.

HolisticBear · Jul 6, 2017

saltyfilmfolks said:
Thank you. As I thought.
That kills internet rumor.
Again.

???

A whole shrimp is a pretty specific example, isn't it? Is throwing in a whole shrimp that isn't decomposing and expecting it to instantly add PO4 a thing on the internet?

saltyfilmfolks · Jul 6, 2017

MrMichael said:
???

A whole shrimp is a pretty specific example, isn't it? Is throwing in a whole shrimp that isn't decomposing and expecting it to instantly add PO4 a thing on the internet?

We feed mysis shrimp and other flesh based items. Each Would need to break down over time to produce a to produce detectable Phosphate.
So Feeding should not produce an immediate increase in testing.

Thus the internet rumor of "I fed to much yesterday and got a huge spike in my Po4". Rather common.
In fact, even over the course of a week this should likely not be the case. IME its actually weeks.

HolisticBear · Jul 6, 2017

saltyfilmfolks said:
We feed mysis shrimp and other flesh based items. Each Would need to break down over time to produce a to produce detectable Phosphate.

True, except that many/some people don't feed like that at all and use 100% prepared foods. Things that have been frozen, liquid, and preserved for months. The bottle of liquid fish roe that's in my fridge and has a good until date of 5 months for example.

Randy Holmes-Farley · Jul 6, 2017

If something eats a shrimp (like a fish), it will be hours until the phosphate is released, not days.

saltyfilmfolks · Jul 6, 2017

MrMichael said:
True, except that many/some people don't feed like that at all and use 100% prepared foods. Things that have been frozen, liquid, and preserved for months. The bottle of liquid fish roe that's in my fridge and has a good until date of 5 months for example.

I am referring to prepared foods. In either case regardless of fresh or frozen the process is the same. its flesh, bones and shells. the source wont matter.