Keep bottoming out phosphate but still nitrates.

Scorchx1245 · Mar 11, 2019

I keep bottoming my p04 out I feel. I was dosing phosphate and got up to .06 (red sea)so I slowed it down, and I'm bottomed out again. But my nitrates still hang around 20-25 (sailfert). I cant seem to find a harmony. The picture doesn't really do it justice I mean the test water is pretty much crystal clear but obviously starts off with color but clears up within the 15 minute test time. Anyone got any suggestions?

Scorchx1245 · Mar 11, 2019

Maybe .01 but at 0.0 its clear. Side note I do dose nopox.

Dkeller_nc · Mar 11, 2019

I'm afraid I'm not at all familiar with the Red Sea phosphate test, so I'm not going to be all that helpful on that front.

But there's quite a number of reasons why you might have all of the phosphate in your water be consumed and your nitrates remain relatively stable. The redfield ratio is 106:16:1 Carbon:Nitrogen

hosphorus, which is a measure of the ratio of elements in phytoplankton in the deep ocean. Whether or not that's a useful ratio to represent fish, coral and macroalgae biomass in a reef tank is debateable. But it's likely that the ratio of C, N & P in the animals that we keep isn't gigantically different. And ignoring for the moment that the expected incorporation ratio of carbon, nitrogen and phosphorus into bacteria that get skimmed out, algae growth, and animal biomass is being expressed as the isolated element in the redfield ratio (instead of organic carbon to nitrate to orthophosphate, for example), you can see that quite a lot of phosphate will be consumed to "make a dent" in the nitrate concentration of the tank water.

Scorchx1245 · Mar 11, 2019

Appreciate it, should I start dosing p04 again? Or feed a bit heavier?

Dan_P · Mar 11, 2019

Scorchx1245 said:
Appreciate it, should I start dosing p04 again? Or feed a bit heavier?

Are you saying that the test color fades during the period of time that it is suppose to be developing? If so, there is something wrong with the test.

Dkeller_nc · Mar 11, 2019

Well, to offer any advice on that front we'd like to know what you have in the tank (SPS, LPS, Softies, what sort of fish load, etc...), how long the tank's been setup, what do you feed (flake, pellets, frozen, etc...), and probably most importantly, do you have a specific problem you're trying to solve, like algae growth, cyanobacteria, etc...

lapin · Mar 11, 2019

Dkeller_nc said:
Well, to offer any advice on that front we'd like to know what you have in the tank (SPS, LPS, Softies, what sort of fish load, etc...), how long the tank's been setup, what do you feed (flake, pellets, frozen, etc...), and probably most importantly, do you have a specific problem you're trying to solve, like algae growth, cyanobacteria, etc...

You want all that? * - }

Dkeller_nc · Mar 11, 2019

Well, one example of why would be if the OP has a major algae issue in the main display tank. In that circumstance, and if it were my tank, I wouldn't dose phosphates, since that's likely to make the issue far worse. Especially if it's a new tank, I would manually harvest as much as possible, and do several major water changes and evaluate from there.

On the other hand, if this is an SPS tank, with no major algae issues in the main display, and it has a refugium, I probably would dose phosphate to fuel the algal growth in the 'fuge.

Scorchx1245 · Mar 12, 2019

Mixed reef. And yes the test says wait 15 minutes and compare results. I have acros, millis, RBTA, euphylia, pavona, etc. Livestock is 2 clowns a baby foxface, and and baby tomini tang, they'll be going to my 300. But my powder brown is an *******. So they they need to grow.

Scorchx1245 · Mar 12, 2019

The test kit expires in 2021. I have some Gha but just went through a tank crash lost a couple acros, birdsnest and my hammer lost s head, the crash was from nopox stopping cold Turkey on vacation and my Ato running out(12 day vacation) my tank sitter never showed up....nitrates and p04 went through the roof cyano went rampant and took me 3 months to rebound. Almost all the cyano is gone. Tank is looking really good but I'm not getting the growth that I was.

Dkeller_nc · Mar 12, 2019

So based on that information, I'd say it's a 50/50 choice. Dosing phosphate may help to lower the nitrates since you're carbon dosing (and presuming that you've a good skimmer and/or mechanical filtration that's running 24/7). But it may also fuel the GHA.

I guess my personal choice if it was my tank would be to feed coral foods (like Reef Roids, PhytoFeast, OysterFeast, etc...) and closely monitor the phosphate and nitrate over a period of a few weeks. The coral foods will (potentially) directly benefit your corals, and will also act to increase the phosphate input into the tank.

MabuyaQ · Mar 12, 2019

Dkeller_nc said:
So based on that information, I'd say it's a 50/50 choice. Dosing phosphate may help to lower the nitrates since you're carbon dosing (and presuming that you've a good skimmer and/or mechanical filtration that's running 24/7). But it may also fuel the GHA.

I guess my personal choice if it was my tank would be to feed coral foods (like Reef Roids, PhytoFeast, OysterFeast, etc...) and closely monitor the phosphate and nitrate over a period of a few weeks. The coral foods will (potentially) directly benefit your corals, and will also act to increase the phosphate input into the tank.

I would not add more Nitrogen in the form of coral food (or any food) with nitrates at 20-25.
When carbon dosing to stimulate bacterial consumption of N those bacteria also need P. With low PO4 you might still be starving thes bacteria and not see a reduction in nitrates.
I would start continue dosingg PO4, but only after this PO4 was confirmed by a different testkit. The reason why you sre having trouble keeping PO4 levels up is because it tends to precipitate onto Calciumcarbonate surfaces, and with all the rockwork and possibly sand in your aquarium it is going to take time untill this proces of precipitation slows down to the point that PO4 dosing results in stable and predictable results.

Dkeller_nc · Mar 12, 2019

I'm afraid he can't avoid putting more nitrogen in the system, unless he wants to starve his fish. It's possible that the reason he's got such low phosphate is that it's simply being taken up by algae. That occurs in one of my tanks - it consistently tests "0" on the Hanna molybdenum phosphorus/phosphate meters (both the 713 and the 736). Yet there obviously is phosphate in the system, since it's being added daily via fish food, and it's very doubtful that all of it is being removed by skimming. Yet the corals do well in this system, despite ultra-low phosphate in the water; I attribute that to coral feeding, but it's possible that additional factors are in play in that system since it has been running since 2004.