# Different sources of NPK



## darkswan (Nov 13, 2004)

Hi all!

While wandering in a local gardening retailer, I found a product made for orchids.
Readings are:

Fe: 0,030%
B: 0,010%
Mn: 0,010%
Mo: 0,001%
Zn: 0,002%
Cu: 0,002%

Well... More dilueted than TMG but not bad in mix and proportions...

My question is regarding macros:

K: 8% K2O
P: 4% P2O5
N: 1,2% N nitric (shoudl be NO3, comeone confirm?) + 2,8% urea

I was asking myself if this could be suitable for our planted tanks. In particular after reading Kekon's valuable reasonings and experiences, I realized that even urea, in small doses, could be appreciated by plants as a different source of N for plants (mind Flourish Nitrogen!).
But I really have no idea concerning K2O and P2O5. Can aquatic plants take K and P in those two compositions? Can they somehow hurt our tanks or have bad impacts?

Many thanks to who may help!


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## hoppycalif (Apr 7, 2005)

The actual compounds in that fertilizer are very unlikely to be K2O and P2O5. The rules for terrestrial fertilizer packaging require that the amounts of potassium and phosphorous be stated as equivalents of K2O and P2O5. Personally, I wouldn't put any such fertilizer in an aquarium. Urea is just not the form of nitrogen that works best for our purposes. Much better to find sources of KNO3, and a phosphate compound to use for macro nutrients.


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## darkswan (Nov 13, 2004)

Thanks for your reply calif!

As you properly remarked, the content of P and K inside the bottle of a terrestrial fertilizer must be stated in terms of P2O5 and K2O respectively. This must be a legal requirement, I guess...
But how can we know what is the real form of P and K inside the bottle?
Let's assume to really pour P2O5 and K2O into our tank. Could they be taken by plants or not?
And how much P (K) would bring 1 ml of P2O5 (K20)?


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