Potassium

[noddin0ff]

Can anybody tell me what the appropriate levels (mg/L or % wt/vol) of potassium is generally used as fertilizer in a planted aquarium and what form the Potassium is supplied in? I work in a molecular biology lab and would like to make my own fertilizer for my tank. Any recipies? Thanks,

noddin

 

[kingborris]

a target level suggested by many is 20ppm

There are a few sources of potassium available for the aquarium. Personally I use potassium sulphate (K2SO4) powder, but KNO3 or KCl will also work fine. KNO3 will obviously add nitrates as well though.

This site has some useful info: http://www.rexgrigg.com/./dosing.htm

and Chucks calulator is very handy: http://www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm

 

[Oldsan]

These change a litlte according to the fashion of the day and the person you ask, but generally the following concentrations seem to be most recommended by the "plant gurus":

NO3: 10 - 25 ppm
PO4: 0.5 - 2.0 ppm
K+: 10 - 30 ppm
Fe: 0.1 - 0.5 ppm (assuming you're using a standard chelated trace mix, this level will assure the other trace elements are correct as well)

Ca/Mg: don't know, but a GH of 3 or more degrees is commonly recommended

CO2: 15 - 30 ppm is considered optimal (lower light = lower value, higher light = higher value), but plenty of plants will continue to grow with lower levels than this obviously. Co2 higher than 30 might hurt fish and there is some talk that plants don't take up more CO2 with higher concentrations anyway.

With low light non-Co2-injected tanks you aim for the same concentrations but you have to dose much less frequently.

 

[gan]

NO3: 10 - 25 ppm

This level is good for plants, but not to good for apistos.

GAN

 

[Oldsan]

I've kept cacatuoides, borelli, and most recently agassizii in tanks with a relatively constant NO3 level of 10 ppm, occasionally higher. Most lived long healthy lives and produced many fry. I'm not an apisto expert by any stretch, but I have noticed over the years without exception that fish do well when plants do well.

 

[noddin0ff]

Thanks for the replies. Seems K2S04 is the way to go. How do you determing ppm of K? Should I worry about it or just dose conservatively and see how it goes?

edit: when I ask how do you determine ppm of K, I don't mean how do you determine how much you add, I mean how do you determine what the existing levels are. Or can you assume that it gets consumed if not added? Where does the SO4 go?