Understanding NPK's - The Planted Tank Forum
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post #1 of 4 (permalink) Old 01-25-2016, 09:35 PM Thread Starter
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Understanding NPK's


I just set up a planted 60 gallon tank and I have a few question regarding fertilizing NPK's.

My Tank:

60 Gallon 48W x 13D x 24H
Flourite 2.5" brown substrate
160 GPH Marineland canister filter with spraybar(Low Surface Agitation)
5lb CO2 system with about 3 bps dissolve rate
1 - 48" 7000k RAY2 FINNEX LED (8 hrs per day)
1 - 30" 7000k RAY2 FINNEX LED (From previous tank, 10 hrs per day)
Topless(No lid)
Lots of driftwood
About 15 assorted African Cichlids
Fertilize with Flourish Comprehensive, trace, and potassium

Current readings:
76 degrees F
Ammonia 0.25 ppm
Nitrate about 15 - 20 ppm
Nitrite 0 ppm
Phosphate 0.25 - 0.5 ppm
GH 322 ppm
KH 286 ppm (taken right before CO2 shuts off at night)
PH 7.6

Would I get any benefit using the flourish nitrogen and flourish phosphorous products? From my understanding, having a decently stocked tank provides plenty of nitrogen(from nitrate) and phosphorous(from phosphate). My plants currently have quite a bit brown algae(diatoms?) but I'm hoping its from my new tank(Set up about a month). Thanks for any comments!
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post #2 of 4 (permalink) Old 01-26-2016, 01:43 AM
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Edit: Haha, unless you edited your post after I posted, I majorly failed at reading. As Diana stated your nitrates are probably ok, adding a little more po4 wouldn't be a bad idea.

It is correct that fish food/waste provide some amount of nitrogen and phophate, but unless you are testing for these levels its all a guess. At some point the demands of your plants will not be met by the amount of food/waste being added to the tank. When adding co2 and a decent amount of light you are generally going to need more nutrients than you are adding via fish food/waste. Adding a little extra N and P and not needing it is not going to cause you any issues. Not adding more N and P and needing it will cause deficiencies in the plants and potentially algae issues.

The diatoms are a normal issue in newly setup tanks. Frequent water changes helps but it will normally run its course.
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Last edited by nilocg; 01-26-2016 at 06:01 AM. Reason: Fsasdfas
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post #3 of 4 (permalink) Old 01-26-2016, 02:41 AM
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Fish food supplies N, P and most traces.
You reported your NO3 as 15-20 ppm. Is this right before a water change? The max it ever gets? If so, this is OK. I would not dose KNO3.
You reported your PO4 as under .5, I would dose just a little KH2PO4 or Flourish Phosphorus.
I would not dose traces.
Fish food is low in potassium and iron. Just dose these. K2SO4 or Flourish Potassium, and chelated iron or Flourish Iron.

If the NO3 regularly gets down into single digits, or hits zero, then the plants are using quite a bit of the NO3, and you could dose some N, P and traces.

Flourish Comprehensive is traces.
Flourish Trace is traces. Do not dose both of these. These plus fish food could result in too-high levels of traces.

Do not worry about the high GH. The fish are fine. But if you really want to do something about it....
What is the GH out of the tap? If it is a lot lower, then do small, frequent water changes to lower the GH slowly. Allow the fish a chance to adapt. It might take several weeks or a month to get the GH down around 200ppm.
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post #4 of 4 (permalink) Old 01-26-2016, 03:46 PM Thread Starter
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The Nitrate in my tap is about 9 ppm(crazy, right?). Before weekly water changes is when it reaches close to 20 ppm. So they stay within 10 - 20 ppm. I plan on adding many more plants(working out compatibility between fish and plants), so the demand will be increasing. I unfortunately do not have an Iron test kit. I am using Flourite as my substrate, which apparently supplies the plants with Iron. Do you think I should still does? And I know that Comprehensive has traces in it as well, but with my high tap water Nitrates, and Comprehensive adding to it, I am dosing a small amount of Comprehensive, and a larger amount of Trace. The tap water has the same GH reading. I am new to hard tap water, so I just wanted to make sure that the fish and plants won' mind it.

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fertilization, fertilizer dosing, fertilizer schedule, flourish, npk

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