PO4 getting sucked up faster - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 01-07-2016, 08:53 PM Thread Starter
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Question PO4 getting sucked up faster

Hi guys,

I measured my PO4 today and I realized that it was getting used up way faster than before. I measured it this morning and it was < 1ppm, closer to 0.5. I used to get away with doing only once a week, (maybe twice sometimes) like only 150mg or around there. This would give me around 1.5 ppm and just fish waste would keep it around there for the entire week.


I really thought this was enough since I only have 2wpg light and DIY CO2 which doesn't give much over 25ppm CO2. But I've been having problems with GSA for a while now but I didn't connect this to PO4 until someone on here said I should up it a few ppm's and start doing twice a week.

Anyone know what could be causing PO4 to get used up faster? I haven't added any plants or anything recently.
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post #2 of 6 (permalink) Old 01-08-2016, 12:45 AM
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Four things off the top of my head.

Error in measurements making the uptake seem greater then it is.
Increased plant mass with growth, requiring an increase in PO4.
Semi-related to the above, a better balance of other nutrients, causing an increase in growth and hence, an increase in PO4 uptake.
Some other issue causing PO4 to precipitate faster.

Feel free to edit.
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post #3 of 6 (permalink) Old 01-08-2016, 12:52 AM
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I think Audio hit it- all these or in any combination.

Do not dose iron and phosphorus on the same day. (these are the most common ones that will precipitate)

Spread out the dosing so there is something closer to an even supply of all the nutrients through the week- some get locked up in the substrate pretty fast.

Increase the dosing, perhaps dose the same amount, but do it twice a week instead of once. (just not on the same day you dose iron).
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post #4 of 6 (permalink) Old 01-08-2016, 01:55 AM Thread Starter
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Quote:
Originally Posted by Diana View Post
I think Audio hit it- all these or in any combination.

Do not dose iron and phosphorus on the same day. (these are the most common ones that will precipitate)

Spread out the dosing so there is something closer to an even supply of all the nutrients through the week- some get locked up in the substrate pretty fast.

Increase the dosing, perhaps dose the same amount, but do it twice a week instead of once. (just not on the same day you dose iron).
Yeah I know about the iron thing so I've always done them at least 12h apart. But spreading out the dosing of KH2PO4 to the same amount ( maybe a bit more) twice a week sounds like a really good idea. Hopefully get PO4 to around 2-3 ppm.

Dosing only once a week was probably the problem then since there's like at least 2x as much plants as when I started.

The other thing Audio said is probably a factor too. I switched from flourish to CSM+B a while back. So the balance of iron and other micros to the macros probably improved.

Last edited by The Coffee; 01-08-2016 at 07:55 AM.
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post #5 of 6 (permalink) Old 01-08-2016, 02:56 AM
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Often things going on in a tank are not due to any one thing, but a combination of several things.
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post #6 of 6 (permalink) Old 01-08-2016, 07:59 AM Thread Starter
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Quote:
Originally Posted by Diana View Post
Often things going on in a tank are not due to any one thing, but a combination of several things.
True that. Like in any kind other kind of dynamic system, it seems you will rarely find a single factor causing some change.
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