Low phosphate

[Mar]

What are some reasons for low phosphate?

Bare bottom 120, medium bio load, 1year old.
I have been struggling with higher nitrates and resulting green hair algae. Ihave been vodka dosing to lower the nitrates however, it has not seemed to lower nitrate as well as I would like. Green hair algae was starting to get a bit concerning when about a month ago it seem to die back pretty quickly.
testing the phosphates I discovered it was at zero and started dosing Neophos at 1 to 2 mls a day which made a big difference in coral health

I feed pretty heavy, 3–5 cubes of brine/Misys per day plus some pellets.

I don’t particularly like having to dose Phosphates and was wondering if there were specific reasons for high nitrate, low phosphate imbalance. Thanks.

 

[T-J]

Depending how bad the GHA is, that would indicate that you have phosphates. They are likely testing low/zero because the GHA is sucking them up as they are being produced.

 

[Dburr1014]

Vodka dosing is not removing nitrates as much most likely it is po4 limited.

Refugiums can lower po4.
Corals can lower po4.
Even rocks can lower po4 if it's sucking it up.

To raise phosphates you can feed more flakes pellets and reef roids.
To lower nitrates why don't you just do some water changes?

 

[Mar]

While water changes would certainly work to correct the imbalance I’m mostly curious as to why the phosphates dropped so much versus the nitrates staying so high (75 ppm). The gha amount dropped by 80% (which I’m assuming is being limited by low phosphate)and has been steady for the last couple weeks even with dosing neophos. I had been using poly filter, but pulled that out when I saw that my phosphates were low.

if the Rocks are absorbing it will they reach a point of saturation?

 

[92Miata]

I don’t particularly like having to dose Phosphates and was wondering if there were specific reasons for high nitrate, low phosphate imbalance. Thanks.

The reason for that imbalance is phosphate deficiency. Once you start depriving the tank of phosphate, it can't process nitrate anymore, and nitrate levels start going up. Dose phosphate long enough that it stabilizes above zero, and the nitrate will come down.

Why do you not like dosing phosphate? Its no different than dosing alkalinity or any other thing the tank needs.

 

[Dburr1014]

if the Rocks are absorbing it will they reach a point of saturation?

Correct.
Rocks will leech and they will absorb po4 to be balanced with the water colum.

 

[Randy Holmes-Farley]

The phosphate dosing seems an appropriate plan. When the Neophos runs out, you can get DIY food or reagent grade sodium phosphate from Amazon for less cost with a purity assurance the Brightwell lacks.

 

[Mar]

Thanks all
I think I figured out the answer I was looking for (as well as the question I was trying to ask).
I’m suspecting the polyfilter was complicit in removing phosphate and once it got too low, created the imbalance cycle as someone pointed out. I’ve always used poly filter as opposed to GFO because it seem to be less aggressive than other phosphate removers.

Time to rethink my nutrient export strategy

 

[Randy Holmes-Farley]

I’m suspecting the polyfilter was complicit in removing phosphate and once it got too low, created the imbalance cycle as someone pointed out. I’ve always used poly filter as opposed to GFO because it seem to be less aggressive than other phosphate removers.

It is far less effective than GFO. It won't take out any inorganic phosphate from seawater. It will bind some organic matter and possibly prevent it from breaking down to inorganic phosphate.