Phosphate

rs1831 · Sep 4, 2015

Is there an ideal time to test to get an accurate measurement?

Best,
Roland

Randy Holmes-Farley · Sep 4, 2015

For phosphate? No, phosphate levels do not change noticeably day to night.

The main one that changes up and down in 24 h is pH.

swk · Sep 4, 2015

If I want the most accurate reading, without foods influencing the measurement, i don't feed for a day and then check the following morning. Do I have any facts or scientific evidence to back this up - NOPE. But, it makes sense in my head...so it's what I do. Rarely am I that concerned with po4 though.

Randy Holmes-Farley · Sep 4, 2015

swk said:
If I want the most accurate reading, without foods influencing the measurement, i don't feed for a day and then check the following morning. Do I have any facts or scientific evidence to back this up - NOPE. But, it makes sense in my head...so it's what I do. Rarely am I that concerned with po4 though.

How often do you feed normally?

I feed a few times a day, and so waiting an abnormally long time before measuring phosphate would seem to result in an unusually low reading, would it not?

Wouldn't you want to know what it usually is rather than what it might become in the absence of feeding?

swk · Sep 4, 2015

Randy Holmes-Farley said:
How often do you feed normally?

I feed a few times a day, and so waiting an abnormally long time before measuring phosphate would seem to result in an unusually low reading, would it not?

Wouldn't you want to know what it usually is rather than what it might become in the absence of feeding?

Like I said - it's just what i do, and I don't expect it to stand up to the rigors of scientific examination. But to answer your questions I feed the fish 2x a day. Pellets in the am and rods food in the pm. The corals get broadcast feelings after lights out 3-4x a week

To me, I like to know what the water is reading minus the addition of feeding. Just to see what is there in the rocks and sand and separate that from what's being added by the food. Is my line of thinking not correct here? I AM a contractor and not a scientist [emoji6]

Randy Holmes-Farley · Sep 4, 2015

I expect that the longer you wait without feeding, the lower it will get, until the photosynthetic creatures in the tank and other export methods can no longer remove any more.

Have you ever measured it in a normal day and seen how much different it actually is than waiting a day without feeding?

swk · Sep 4, 2015

Yeah, it's a bit lower but not by much. I'm more of a "dirty" tank fan for my sps. I prefer it to be around. .06-.1

More often than not I'm testing my gfo reactor effluent to see if it still has life left in it.

Randy Holmes-Farley · Sep 4, 2015

Sounds good.

Happy Reefing.

rs1831 · Sep 6, 2015

Thank you for the feedback. My tank is about 8 months old at this point and I am having issues keeping sps. I feel that my alk has been very stable now since adding a doser and it has been that way for 4+ months. Everything else seems stable as well. I have good flow and lighting. This makes me feel that I have been starving my corals with 0 phosphates and that I was over using gfo and larger than needed weekly water changes.. About 3 weeks ago I took the gfo off line and started doing more appropriate water changes while slowly adding more food. Over the last week or so I have been measuring between 10-12 with a Hanna phosphorus checker. What would be a good game plan on keeping the phosphates in the .03-.06 range? How do others use gfo so that phosphates do not drop to zero but do not get out of hand?

Best,
Roland

Randy Holmes-Farley · Sep 7, 2015

rs1831 said:
Over the last week or so I have been measuring between 10-12 with a Hanna phosphorus checker. What would be a good game plan on keeping the phosphates in the .03-.06 range? How do others use gfo so that phosphates do not drop to zero but do not get out of hand?

For each aquarium it is a balance between input and output. Between feeding and the various uptake and export methods. If you monitor phosphae through a couple of GFO cycles, you may get a better idea how much you need and how often to change it. The value now seems fine if you do not have an algae problem.

rs1831 · Sep 7, 2015

Randy, thank you for your input. What level do you try to keep phosphates at? Is your goal with gfo to zero out phosphates or to lower them and then to stop using it.

Thanks

Randy Holmes-Farley · Sep 7, 2015

I would usually aim for 0.02 to 0.03 ppm phosphate unless you have an algae problem (then lower).

Unfortunately, many kits cannot read that low, so they would just give a 0 ppm.