# How does fish waste affect fertilzing routine?



## Oreo (May 16, 2008)

Specifically... Without fertilizing I can't seem to get my nitrates below about 20ppm with water changes. So I'm looking at the bags of dry ferts I just bought & realized I probably don't need the KNO3 (potassium nitrate) at all since the KH2PO4 (mono potassium phosphate) seems like it should handle the other two macros just fine and my fish supply the nitrate. Is this correct thinking?

Besides carbon, which macros are used the fastest- in what order, I mean?


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## ray-the-pilot (May 14, 2008)

Oreo said:


> Specifically... Without fertilizing I can't seem to get my nitrates below about 20ppm with water changes. So I'm looking at the bags of dry ferts I just bought & realized I probably don't need the KNO3 (potassium nitrate) at all since the KH2PO4 (mono potassium phosphate) seems like it should handle the other two macros just fine and my fish supply the nitrate. Is this correct thinking?
> 
> Besides carbon, which macros are used the fastest- in what order, I mean?


I do not recommend any plan that does not require some water changes each week. I would follow the plan you have chosen exactly! If it is EI you will need to do 50% water changes per week. If you use EI you should have no problem with build up of NO3

I use PPS pro but do 20% water change each week.

If you find that Nitrates are building up with PPS pro just do extra water changes to bring them down.

Aquatic plants use K and NO3 about the same an PO4 the least.


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## Zapins (Jul 28, 2004)

Light, water, CO2, O2, nitrogen, phosphate, potassium, calcium, sulfur, and magnesium, traces... is the order plants use nutrients fastest.


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## Oreo (May 16, 2008)

My setup is a bit different. I'm running a constant tap-water drip system w/overflow to drain. The aquarium is about 75gal and the drip is about 1gph. In short, I get about two full water changes per week, sometimes a little less. 

My bio-load is kinda heavy though:
1 huge goldfish (9"!!)
1 huge black ghost knife
1 cichlid
1 Coryadora
1 silver dollar
10 or so molly's and about a hundred fry 'cause they breed like crazy.
a patriot crab and a newt of some kind. Oh, and a guppy.

(I've got a beast of a filtration system & everyone seems to get along fine in the tank.)

BUT, I'm new to aquaculture. First I was told it was impossible in my tank because of my livestock. 6 months later though I've found many plants will grow just fine as long as I do my part- which I'm learning slowly.


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## Oreo (May 16, 2008)

Zapins said:


> Light, water, CO2, O2, nitrogen, phosphate, potassium, calcium, sulfur, and magnesium, traces... is the order plants use nutrients fastest.


Since plenty of potassium comes along with the phosphate would Calcium Nitrate be a better choice then Potassium Nitrate? Magnesium sulphate & a trace mix could be used to finish things off.


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## ray-the-pilot (May 14, 2008)

Zapins said:


> Light, water, CO2, O2, nitrogen, phosphate, potassium, calcium, sulfur, and magnesium, traces... is the order plants use nutrients fastest.


I believe you but my experience with PPS pro confuses me.

When I dose at the rate of 1 ppm of K and 1 ppm of NO3 and 0.3 ppm of PO4 my water column pretty much stays in balance when I test for the three. Why do you think this is?


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## Zapins (Jul 28, 2004)

ray-the-pilot said:


> When I dose at the rate of 1 ppm of K and 1 ppm of NO3 and 0.3 ppm of PO4 my water column pretty much stays in balance when I test for the three. Why do you think this is?


I'm not sure what you mean exactly?


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## surpera1 (Feb 18, 2009)

50 % water change per week with EI - you might be displacing your nutrients too quickly with that much water change


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## Zapins (Jul 28, 2004)

Oreo I found an interesting bit of information recently that might help answer your question about what proportions nutrients are found in plants.

The diagram below will vary from plant to plant, and some prefer a bit more or less of one nutrient or another. There is no magic bullet that will grow all plants.


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## niko (Jan 28, 2004)

2 things to consider maybe:

1. Some years ago I experimented with about 7-8 different kinds of food. Dry and frozen. I could not find a single kind of food that increased both the N and P. All of them increased N - some more some less. The P was increased very little, with most foods not at all. I ran the tests 2 days after feeding.

2. Nice numbers Zapins! But I do not believe in chasing numbers. Observe the plants and fertilize/act accordingly.

--Nikolay


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## clearleaf (Oct 4, 2008)

That's an interesting chart. There are some wide spectrums there, though. I mean I understand there's no magic bullet [edit: and the important data points to take away are the ratios], but between 0.3% and 6.0% is kind of...wide. Or 10 to 1500 ppm. Can I ask where you found this out of curiosity?


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## Zapins (Jul 28, 2004)

Aquatic Horticulture by Karen Randall from November 1997
http://www.csd.net/~cgadd/aqua/ah_main/nov1997.html

The chart shows dry weight. In other words, after a plant has been dried out completely it was tested for concentrations of various elements and the concentrations were put into that chart.

Also, 0.3% to 6% is 10-200 ppm, not 10-1500 ppm. You are right about the chart being useful for the ratios between elements.

I just want to point out that I don't think the chart can be used as a direct reference for what ppm concentrations to keep in the aquarium. For example, if you have 0.5 ppm nitrate in a lake that has 200,000 gallons vs. a planted tank with 10 ppm nitrates, there are still a heck of a lot more nitrates in the lake than the tank. The plants will grow perfectly well in both places. The reason we like to keep detectable levels of nutrients in our tanks is because since the volume of water is less than a huge lake if we try keep 0.5 ppm nitrates in there the plants will very quickly remove it from the water column and then starve, but in a huge lake they will take years to remove this concentration.


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## clearleaf (Oct 4, 2008)

Yea sorry, I was actually pointing at two different values, the potassium (0.3-6.0%) and the iron (for the 10-1500), just at random. And thanks for the link, that's a very interesting article. I really liked this, "Studies have shown that plants can take up the total amount of phosphate available in a lake in two minutes, while it is replaced at an equivalent rate by decaying organic matter." Fascinating concept.

As for the OP, you *could* try calcium nitrate instead, I believe it has a slightly smaller ratio of nitrate per weight. Or just drop it altogether and see what happens. I wouldn't rely on KH2PO4 for a potassium source, though, the amounts you are dosing in PPS are for phosphate and it doesn't yield much K. Maybe drop KNO3 and add K2S04, if you aren't already. Hopefully someone can back me up, because my chemistry isn't that great, but this is my guess.

However I really wouldn't do any of that. I think Niko's advice is spot-on: if the plants and fish are happy then I wouldn't worry about the nitrate levels. (Or just add more plants!)


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