PO4 too low

Jizu Puentes · Feb 13, 2016

I added a 135 gallon to my system two weeks ago and I've just completed the first parameter tests on the system. On the day I set up the tank I added Rowaphos so I tested the phosphate level today to see how it is working. It seems to be working a little too well. I tested with a salifert PO4 test kit and performed the test at double sensitivity and got no reading at all. I'd like for my levels to be at least detectable so I am wondering if I should remove the Rowaphos or wait for the levels to rise with it in. Also what do you guys prefer PO4 to be at in your tanks?

Randy Holmes-Farley · Feb 14, 2016

I am not sure how low that implies phosphate is, and whether it necessarily is "too low", but if you want to raise it, using less GFO, less flow through the GFO (if it is not already very low), or replacing it less often sound like appropriate plans.

I generally recommend about 0.02 ppm phosphate as a reasonable target unless you have an algae problem, in which case lower is good.

I discuss it here:

Phosphate In The Reef Aquarium
https://www.reef2reef.com/blog/?p=3184

Jizu Puentes · Feb 14, 2016

Randy Holmes-Farley said:
I am not sure how low that implies phosphate is, and whether it necessarily is "too low", but if you want to raise it, using less GFO, less flow through the GFO (if it is not already very low), or replacing it less often sound like appropriate plans.

I generally recommend about 0.02 ppm phosphate as a reasonable target unless you have an algae problem, in which case lower is good.

I discuss it here:

Phosphate In The Reef Aquarium
https://www.reef2reef.com/blog/?p=3184

I'm thinking that it is too low because it measures zero for the normal test and double sensitive test and I've seen a fading of color in some of my coral. I wouldn't say I have algae problems but i do have little groups of bubble algae in sparse areas and the low phosphates dosent really seem to bother them. Do you think I should leave my current amount of gfo in until I see a rise or should I take it out now, let the phosphates rise, then add gfo again but in less amounts?

Randy Holmes-Farley · Feb 14, 2016

Jizu Puentes said:
I'm thinking that it is too low because it measures zero for the normal test and double sensitive test and I've seen a fading of color in some of my coral. I wouldn't say I have algae problems but i do have little groups of bubble algae in sparse areas and the low phosphates dosent really seem to bother them. Do you think I should leave my current amount of gfo in until I see a rise or should I take it out now, let the phosphates rise, then add gfo again but in less amounts?

It might be, and it is fine to experiment, but fading might be for other reasons, such as low nitrate. How long ago did you add the GFO?

Valonia (bubble algae) is a species that seems to do OK at lower nutrient levels and is hard to eradicate with low nutrients.

Jizu Puentes · Feb 14, 2016

Randy Holmes-Farley said:
It might be, and it is fine to experiment, but fading might be for other reasons, such as low nitrate. How long ago did you add the GFO?

Valonia (bubble algae) is a species that seems to do OK at lower nutrient levels and is hard to eradicate with low nutrients.

I added the GFO on Sunday Jan31st. So two weeks ago. I think I will do some experimenting. My system is 4 tanks, including the sump, and a little over 300 gallons. I have 14 fish total and one tank, a 110 gallon has dragons breath and chaeto do growing in it. I think I'll remove the GFO and measure every now and then to see what my normal levels. Once i remove the GFO how often do you think I should test?

Randy Holmes-Farley · Feb 14, 2016

I'd expect phosphate to rise within a day or two of removing the GFO, so I'd measure at least every other day for at least the early part of the experiment.

Jizu Puentes · Feb 27, 2016

It's been two weeks since removing the GFO and i am still measuring zero PO4. Im wondering if my macroalgae just uses all the i have so I'm unable to detect it. I feed a frozen blend twice a day but maybe it isn't enough to produce significant PO4?

Randy Holmes-Farley · Feb 27, 2016

Jizu Puentes said:
It's been two weeks since removing the GFO and i am still measuring zero PO4. Im wondering if my macroalgae just uses all the i have so I'm unable to detect it. I feed a frozen blend twice a day but maybe it isn't enough to produce significant PO4?

That is certainly possible. Or the kit isn't working.

Jizu Puentes · Feb 27, 2016

Haha I actually checked for that too. I tested some of my unfiltered well water and the test showed the phosphates. I'll just keep running GFO less for now and check my nitrates.

Randy Holmes-Farley · Feb 27, 2016

Jizu Puentes said:
Haha I actually checked for that too. I tested some of my unfiltered well water and the test showed the phosphates. I'll just keep running GFO less for now and check my nitrates.

Sounds good.

Happy Reefing.

BradB · Mar 2, 2016

I am battling phosphate now, and can't believe this thread. Any time I can measure Nitrate, I measure 0 phosphate, except when my tank looks really bad or just after feeding. No hobbyist test kit is able to distinguish between too low phosphate and optimal phosphate. If you have measurable Nitrate and the 'zeovit' looking pastel colors, you might have too low phosphate - easily fixed by feeding more.

Other than the Hanna ultralow, I bet every hobbyist test kits can measure 0 with water that has too much phosphate.

jason2459 · Mar 2, 2016

BradB said:
I am battling phosphate now, and can't believe this thread. Any time I can measure Nitrate, I measure 0 phosphate, except when my tank looks really bad or just after feeding. No hobbyist test kit is able to distinguish between too low phosphate and optimal phosphate. If you have measurable Nitrate and the 'zeovit' looking pastel colors, you might have too low phosphate - easily fixed by feeding more.

Other than the Hanna ultralow, I bet every hobbyist test kits can measure 0 with water that has too much phosphate.

I found the Elos PO4 Pro kit and Hach to be up to the task.

Jizu Puentes · Mar 2, 2016

BradB said:
I am battling phosphate now, and can't believe this thread. Any time I can measure Nitrate, I measure 0 phosphate, except when my tank looks really bad or just after feeding. No hobbyist test kit is able to distinguish between too low phosphate and optimal phosphate. If you have measurable Nitrate and the 'zeovit' looking pastel colors, you might have too low phosphate - easily fixed by feeding more.

Other than the Hanna ultralow, I bet every hobbyist test kits can measure 0 with water that has too much phosphate.

Yea I guess that if you have any type of algae at all then the phosphate levels will measure zero unless you have an insane amount. I was under the assumption that the macroalgae would use a certain amount and that I'd be able to detect something when testing

Randy Holmes-Farley · Mar 2, 2016

BradB said:
No hobbyist test kit is able to distinguish between too low phosphate and optimal phosphate.

What level do you consider optimal?

BradB · Mar 2, 2016

I am not sure what actual level is optimal. I just know seeing anything on a test kit is usually a problem, and seeing 0 is usually a good thing. In reality, 0 on the test kit is probably a non zero number below the accuracy of the test.