Undetectable Phosphates...what to do?

[Gustavo89]

Hello, ive been dealing with Undetectable Phosphates , normally i test with Hanna Checker.

1 month ago, i move the sand abprutly to test the next day and they were around 0.75 PPM, then checked again after 3 days they were around 0.20 ppm, then again until 0.00 PPM.

So i guess they are precipitated on the sand and rocks, so i start feeding twice per day, and i started turning off the Skimmer after 8 hours working, so i can increment at least to 0.03 PPM.

I have been like this the last month, and i have undetectable phosphates still, Corals are growing ok.

Should i add or modify something? Probably increasing the quantity of fishes to increment the organic waste?

PS, i have 2 wavemakers, its a 110 Galls aquarium working for about 2 years.

 

[BayouReefer]

Are you running GFO?

 

[Gustavo89]

Are you running GFO?

Great question, i forgot to mention it.

I stopped running GFO like 1 month and a half ago, The reactor is still in the sump but completely Turned Off.

Another thing, i have a chaeto refugium that is running for about 11 hours..

 

[BayouReefer]

I know people do sometimes does phosphorus. That is an option how are your Nitrate levels?

 

[Gustavo89]

I know people do sometimes does phosphorus. That is an option how are your Nitrate levels?

Also low! around 5 ppm, this could be because of the 11 hour running Chaeto, and also because of few fishes (around 5) but small to medium size...

 

[BayouReefer]

Forgive me if I ask stupid questions but I am new at this only about a year now so I am learning as I try to think it through. If you started turning your skimmer off some and then you are seeing measurable amounts of phosphate. It could simply be that your system is running very efficiently and you may just be lacking nutrients in your water I. E fish poop and left over food. So how about turning your skimmer off a little longer and see if they come to the level your looking for

 

[BayouReefer]

And are you wet skimming or dry skimming. Is the Skimmate dark green?

 

[Gustavo89]

Forgive me if I ask stupid questions but I am new at this only about a year now so I am learning as I try to think it through. If you started turning your skimmer off some and then you are seeing measurable amounts of phosphate. It could simply be that your system is running very efficiently and you may just be lacking nutrients in your water I. E fish poop and left over food. So how about turning your skimmer off a little longer and see if they come to the level your looking for

yes indeed, i was thinking in doing just 4 hours or 4 of skimming, and im doing dry skimming!

 

[Sallstrom]

Two signs I look for to see if the phosphate is too low is how the corals look(pale corals might be low phosphate for example) and if there is Cyanobacteria(might thrive in low PO4 or NO3).
We run a couple of reef tanks that meassures zero on our Hanna tests. As long as you're feeding the fish and not using a carbon source or GFO (or a too large algae refugium), there's often still enough phosphate in the tank. So if everything is looking fine, I shouldn't change too much.

If you don't have that much fish or don't want to feed more, you can add phosphate. We're using KH2PO4 powder mixed with RO water and have done that for many years now in some tanks. We buy KH2PO4 from a shop for planted freshwater aquariums.

 

[Sallstrom]

Two easy options to try out would be:

1 - let the skimmate go back to the tank (remove the skimmer cup if the skimmer is in the sump)
2 - lower the light hours for the algae refugium as much as needed. The algae doesn't have to grow as fast as possible.

 

[Gustavo89]

Two signs I look for to see if the phosphate is too low is how the corals look(pale corals might be low phosphate for example) and if there is Cyanobacteria(might thrive in low PO4 or NO3).
We run a couple of reef tanks that meassures zero on our Hanna tests. As long as you're feeding the fish and not using a carbon source or GFO (or a too large algae refugium), there's often still enough phosphate in the tank. So if everything is looking fine, I shouldn't change too much.

If you don't have that much fish or don't want to feed more, you can add phosphate. We're using KH2PO4 powder mixed with RO water and have done that for many years now in some tanks. We buy KH2PO4 from a shop for planted freshwater aquariums.

The corals are doing just fine, i have some SPS and they are good.

Actually, i have some Cyano only on the rocks, i increased the power of the wavemakers supposing is for the lack of water flow, should i tackle it first? before dosing phosphate?

The skimmer is in the Sump working only 12 hours a day! (i reduced it from being working 24/7).

What i removed was the GFO Reactor..

Thanks!

PS.- Again should i tackle the cyano first before dosing and so on?