Bizarre PO4

imatrout

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Apr 4, 2005
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I was developing a little GSA in my 150 gal tank so I measured PO4 and it measured at .5 ppm. NO3 is at 25 so I decided to add some PO4.

I added a little less than .25 tsp of KH2PO4 (Fertilator says this ADDS around 1.7 ppm. I waited about an hour and tested the water again and it tested LOWER at .1 ppm. I measured again for sanity sake and it measured the same at .1ppm. It should have been at 2.0 or more. What could have happened besides me screwing up the original test? If PO4 is severly limited, does it get sucked up that quickly?
 

fosteder

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Feb 3, 2005
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Re: Bizarre PO4

What could be happening is a poor test kit. What kind do you use?

I know my PO4 test kit is basically useless (especially for anything higher than 1ppm). It is almost impossible to distinguish between the colors on the guide.

Have you tried making a reference solution using distilled water? If you do this you may find that your test kit is no good.
 

Tom Barr

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Jan 23, 2005
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Re: Bizarre PO4

Uptake is fast, but it appears as pearling, not uptake that fast.
The test kit is toast or you did not add PO4 etc(mixed it up with KNO3 etc).
Declines of 0.4ppm have occurred in a day etc.
Not 1.7 ppm.

Regards,
Tom Barr
 

imatrout

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Re: Bizarre PO4

Thanks guys. I went and got a new PO4 test kit. I was using a Red Sea Kit, and all I could find at the LFS was an Aquarium Pharm PO4 kit. I test the water and I get a reading od 10 PPM !!!!!! That's right, I tested it twice and got 10 PPM. That's not possible as I've only added .25 tsp of KH2PO4 this week in total. (150 gal tank) I just don't get it. The Red Sea kit says I have less than half what I added and the AP kit says I have 3-4 times what I added.

Any ideas? Status: Plants acting better, worried about discus.

Thanks!
 

reiverix

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Re: Bizarre PO4

I'd go with fosteders suggestion and verify against distilled water.
 

imatrout

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Apr 4, 2005
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Re: Bizarre PO4

Wow, I tested it with a Salifert test kit and it's true, the PO4 in this tank was over 10 PPM AFTER a 50% WC. I did another 50 % to try to get it down. Any idea where this PO4 could be coming from? I feed frozen bloodworms (frozen foods sometimes adds phosphate) and added .25 tsp KH2PO4 last week.

I'm amazed, I went from worrying about not enought PO4 to worrying about too much. The plants sure do like it!
 

turbomkt

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Re: Bizarre PO4

imatrout said:
Wow, I tested it with a Salifert test kit and it's true, the PO4 in this tank was over 10 PPM AFTER a 50% WC. I did another 50 % to try to get it down. Any idea where this PO4 could be coming from? I feed frozen bloodworms (frozen foods sometimes adds phosphate) and added .25 tsp KH2PO4 last week.

What's your substrate? Is it possible you have a bad batch of eco-complete? For me with a bad batch two +50% water changes back to back (so at least 75%) still had me at 10ppm on PO4.
 

imatrout

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Re: Bizarre PO4

Turbo

Funny you should mention that. I just changed out my entire substrate to 100% Eco-complete about 2 months ago. I've done lots of WCs since then. It is possible that I have had the high PO4 since I changed substrate and not known it as the Red Sea test kit mentioned above was inaccurately measuring very low PO4. When I changed my substrate I noticed after adding one out of 14 bags of Eco-Complete, the water was milky white so I scooped as much of that bag out as I could.

Whats really wierd is that I started looking closely at PO4 because I had some GSA (typical of low PO4). Is it possible to get GSA with PO4 at 10 ppm?

So what did you do about the bad eco? Are you just living with it?

Thanks
 

imatrout

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Re: Bizarre PO4

One other thing I'm concerned about is the possibility of how the high PO4 can effect the KH/CO2 relationship. Does anybody know how this works and if it;s a concern. I have a KH of 8.5 and set the PH controller at 6.7 Theoretically I shoud be dosing 50 ppm of CO2 per the chart. Could that be or am I really dosing less? and reading it wrong due to the high PO4?
 

turbomkt

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Re: Bizarre PO4

imatrout said:
Turbo
Funny you should mention that. I just changed out my entire substrate to 100% Eco-complete about 2 months ago. I've done lots of WCs since then. It is possible that I have had the high PO4 since I changed substrate and not known it as the Red Sea test kit mentioned above was inaccurately measuring very low PO4. When I changed my substrate I noticed after adding one out of 14 bags of Eco-Complete, the water was milky white so I scooped as much of that bag out as I could.

Sounds like you had a bad batch. I e-mailed Carib-Sea through their web site (after calling and not getting a call-back). The e-mail is [email protected]. Betsey replied to me quite promptly after I described my situation. She asked how many bags I used and the replacement was in my hands within a week. It's almost too bad I'm honest that I only had one bag (10g tank). She sent it to me without proof of purchase.

What some people will have to remember (before taking advantage of Carib-Sea) is that companies will only have good customer service until they are taken advantage of by too many people.

imatrout said:
Whats really wierd is that I started looking closely at PO4 because I had some GSA (typical of low PO4). Is it possible to get GSA with PO4 at 10 ppm?

Can't answer that one. Tom probably can ;)

But I'd have to think that an excess of PO4 but not enough NO3 and CO2 might still induce either GSA or something that looks similar. Dunno.