Zero phosphates even with dosing

[Tyberzann]

Good evening all,

Looking for a bit of advice on some zero phosphate issues I am having.

For the past 4 weeks I have been autodosing Nyos Phosphate + at 10-12ml per day, my tank is around 460-500 litres with rock and sand so that should equate to roughly 0.02ppm a day of phosphate.

Trouble is, using a Hanna ULR phosphorous checker and a ELOS phosphate test I am getting zero phosphate at all in the tank.

I have read that it can take around 1-2 weeks for phosphate to catch up but at this point I have dosed nearly 500ml of the stuff.

I had an ICP at the back end of May but even then my test kits were showing zero,

I feed the tank 4 times a day, 2 frozen and 2 pellets on an auto feeder.

I have SPS in the tank and they all appear fine but concerned about zero phosphates introducing Dinos

Anyone have any suggestions?

 

[TX_REEF]

how much coral is in the tank? what nutrient export are you running? I had this issue on my display and fixed it by removing my skimmer. I didn't even bother adding a skimmer on my frag system for this reason.

 

[PPBlimpy]

If it is a heavily stocked tank I would bet the corals are sucking up everything you are dosing. taking the skimmer off line for a bit as mentioned may help.

have a refugium with macro? maybe shorten the photo period for a while?

other then increase feeding and dosing more there isnt much you can do.

 

[BriDroid]

I learned that it can take a lot of phosphate dosing to make it show up on a test! I was dosing TONS of it daily and sill had very little show up. At one point I was putting in 0.3 to 0.4ppm trisodium phosphate a day, and the test still would show 0ppm a few hours later. Then one day, it was there. I assume that my rock and sand was sucking in as much as I was putting in until I finally overcame that amount. I do feed Phos-Feed daily too, that way my corals were getting P without it showing up in the water column.

 

[PPBlimpy]

I learned that it can take a lot of phosphate dosing to make it show up on a test! I was dosing TONS of it daily and sill had very little show up. At one point I was putting in 0.3 to 0.4ppm trisodium phosphate a day, and the test still would show 0ppm a few hours later. Then one day, it was there. I assume that my rock and sand was sucking in as much as I was putting in until I finally overcame that amount. I do feed Phos-Feed daily too, that way my corals were getting P without it showing up in the water column.

rock and sand absorbing it is a good thought!i forgot that happens

 

[Randy Holmes-Farley Verified Community Expert]

I’d up the daily dose to 0.1 ppm until you get phosphate values above 0.05 ppm 24 h later.

 

[Tyberzann]

Thanks for all the replies.

For export I currently have a reefmat 1200 and a skimmer. No refugium or algae scrubber as I have not every had high nutrients. right now my Nitrate is sitting at 9.8 so within the 5-10 range I usually keep.

For stock I have the below:

2 clowns
5 green chromis
4 azure damsals
purple firefish
regal tang
Royal Gramma
cleaner shrimp and assorted snails.

For coral I have 8 small sps frags, mainly monti's, Stylophora etc. The easier SPS.

I’d up the daily dose to 0.1 ppm until you get phosphate values above 0.05 ppm 24 h later.

I will give this ago, will have to monitor daily or every other to make sure it doesn't skyrocket.

 

[Randy Holmes-Farley Verified Community Expert]

Phosphate binds to rock and sand as you try to raise it. That may be where most is going, and why it might take large amounts to bring it on scale.

 

[Tyberzann]

Phosphate binds to rock and sand as you try to raise it. That may be where most is going, and why it might take large amounts to bring it on scale.

Yeh I had read this was possible, around 4 months ago the Phosphate was so high that I used GFO, now its so low im dosing. Crazy hobby this haha.

 

[Tyberzann]

Progress update, I have dosed 40ml of Phosphate+ since thursday evening on a auto doser, 24 doses a day equaling 0.1ppm phosphate every 24hrs. Did a phospahte test today and the Hanna checker is showing 16 which works out to around 0.049ppm phosphate.
I am away with work until wednesday so going to lower dosing back to 12ml a day and hope that the level remains elevated.

 

[Randy Holmes-Farley Verified Community Expert]

OK let us know what happens. I'd personally let it run a bit before reducing the dosing, but its likely fine to do so. :)

 

[Tyberzann]

OK let us know what happens. I'd personally let it run a bit before reducing the dosing, but its likely fine to do so. :)

Yeh, im tossing up coming back to 0/3ppm or zero at the moment :). Hopefully the 12ml keeps it stable and ill come back to 16ppm on the Hanna phosphorous ULR!

 

[Tyberzann]

So I tested today, I left the doser adding 12ml of phosphate+ a day whilst I was gone for work.

The test result for today was 38 ppb on the phosphorus test which equates to 0.117 phosphate. So pretty glad I lowered the dose whilst I was gone.

I have done a rough calculation of consumption vs what I have been adding and it looks like I will need to reduce the dosing around 75% further. That way it can drop just below 0.1 and I can maintain that level.

 

[Randy Holmes-Farley Verified Community Expert]

OK, let us know what happens. :)