Phosphates at .54? I dont think thats right...

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For some context, I recently did a hanna phosphate check and it read at .46 the first test and .56 the second. Now of course this is very concerning, but I don't think it's accurate. My tank is 120 gallons, no fish so far and 7 1/2 months old. I'm running GFO and keeping phosphate sensitive coral such as favia and lobophyllia, and while recently I have gotten into the habit of feeding the coral every 2-3 days, I only use ~4 cubes of this really fine coral food
20230913_214749.jpg

So anyways, it's not much. I clean the filter sock every 2 days and everything else seems to be good. Until I tested the phosphate. A reading like that makes no sense considering the little I'm feeding and the amount of GFO I'm running
20230913_214830.jpg

Yep, that bag is full of GFO (to avoid the exact problem of high phosphates, added 100 more ml yesterday) I'm also thinking It could be the testing vial, I clean it with RO, microfiber cloth and a paper towel but it still looks like this
20230913_214605.jpg

Again, the polyp extension on the corals is amazing so I doubt this reading is correct but I do need your opinion, I'm taking a sample in to my LFS to use their hanna/vial but until then I'd like to hear you guys opinion. Thanks!
20230913_220003.jpg
20230913_220006.jpg
20230913_215201.jpg

(Said polyp extension after tonight's feeding,)
 
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It’s probably reading correctly. Plenty of people run successful reef tanks with phosphate over 1.0, no need to run an ultra low nutrient system if coral are happy with higher nutrients.
Though I did test it on Monday and it was at .04, which is where it usually is, high phosphates usually kill my favias, so I hope that wasn't correct..
 

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Check your reagent expiration date but it is very possible the reading is correct. IMO, four cubes is a lot for a fishless system and you don't have much corals either it seems. Rocks absorb phosphate until they hold too much and will then leech it back. My system was running 0 phosphate 0 nitrate for a long time and I had to dose both and feed heavy. Then all of a sudden my phosphate rocketed to 1.2.
 

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Check your reagent expiration date but it is very possible the reading is correct. IMO, four cubes is a lot for a fishless system and you don't have much corals either it seems. Rocks absorb phosphate until they hold too much and will then leech it back. My system was running 0 phosphate 0 nitrate for a long time and I had to dose both and feed heavy. Then all of a sudden my phosphate rocketed to 1.2.
Agree with this and others, it is probably reading correct. One thing to note about your bag of GFO, without proper water going through it or tumbling, it probably isn’t pulling out as quick as that amount should (which can be a good thing since it depletes so quickly).

For context, I have a chemipure elite small size in my 10 gallon which goes through a Aquaclear 110 hang on back filter, it definitely passes by the GFO, but not aggressively so it doesn’t strip the water fast (again a good thing in my case).
 
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Check your reagent expiration date but it is very possible the reading is correct. IMO, four cubes is a lot for a fishless system and you don't have much corals either it seems. Rocks absorb phosphate until they hold too much and will then leech it back. My system was running 0 phosphate 0 nitrate for a long time and I had to dose both and feed heavy. Then all of a sudden my phosphate rocketed to 1.2.
I'll check it again this morning, though the cubes are only about half the size of your Normal mysis cubes, and is also why I like to change the filter sock after each feeding
 

ninjamyst

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I'll check it again this morning, though the cubes are only about half the size of your Normal mysis cubes, and is also why I like to change the filter sock after each feeding
are you broadcasting or target feeding? A full tank shot may help but it doesn't seem like you have that many corals....
 

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It doesn’t sound like there’s an actual problem. All coral and fish are happy. Just leave it alone.
Well he might be over feeding, there are no fish. The four cubes in one feeding looks like a lot of food for the few corals.
If there is no coral mass in few months the rocks will be covered in GHA and that is pain to deal with. Those rocks look nice and clean and just invitation for GHA.

I feed lot less probably 1/3 of the one cube and my Favia look like this:
1694741346738.jpeg

1694741376115.jpeg

I don’t have a lobo…
 

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I do not specifically feed my coral anything and they're perfectly happy.

If you don't have any fish to feed I'd be dosing some Nitrate and Phosphate periodically rather than dumping in a ton of food.

FWIW, The Hanna checker may not have received a clean sample - even tiny particulates can invalidate a reading.
 

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For some context, I recently did a hanna phosphate check and it read at .46 the first test and .56 the second. Now of course this is very concerning, but I don't think it's accurate. My tank is 120 gallons, no fish so far and 7 1/2 months old. I'm running GFO and keeping phosphate sensitive coral such as favia and lobophyllia, and while recently I have gotten into the habit of feeding the coral every 2-3 days, I only use ~4 cubes of this really fine coral food
20230913_214749.jpg

So anyways, it's not much. I clean the filter sock every 2 days and everything else seems to be good. Until I tested the phosphate. A reading like that makes no sense considering the little I'm feeding and the amount of GFO I'm running
20230913_214830.jpg

Yep, that bag is full of GFO (to avoid the exact problem of high phosphates, added 100 more ml yesterday) I'm also thinking It could be the testing vial, I clean it with RO, microfiber cloth and a paper towel but it still looks like this
20230913_214605.jpg

Again, the polyp extension on the corals is amazing so I doubt this reading is correct but I do need your opinion, I'm taking a sample in to my LFS to use their hanna/vial but until then I'd like to hear you guys opinion. Thanks!
20230913_220003.jpg
20230913_220006.jpg
20230913_215201.jpg

(Said polyp extension after tonight's feeding,)

1.
You need a new cuvette

Edit: ALSO
I bought some "GFO" on Ebay and it doesn't absorb anything as far as I can tell? Got a huge box and put it in a proper canister filter and it looks like GFO but it doesn't touch phosphate. I have used others that did, just saying, I have seen some GFO that wasn't worth a dime.

2.
Lanthanum chloride
Happy New Year Vote GIF by INTO ACTION
:cool:
 
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