Hi,

I have a heavily planted 50 gallon tank. Plants are amazon, melon and pigmy chain swords, apogenton, cardamine and dwarf sag. I use a lot of CO2, around 30ppm. Everything grows like crazy and I am happy but I have no idea how much potassium I should add as I don't have a test kit. I measure nitrates and phosphates and they are fine and I don't need to add any as fish food is enough. I just add micronutrients every maybe 2 weeks, 1/4 tspn of CSM+B which comes to around 0.5ppm of iron in my tank.

I add 1 tspn of K2SO4 once every two weeks as an insurance but I don't really know if that is enough, that should add 15ppm of potassium in my tank.

I don't change the water at all so I can't do estimative indexing.

The only thing not performing 100% is apogenton, middle of the leaf becomes black and the leafs are constantly dying but the new ones are emerging all the time. I am not sure if this is normal or it indicates potassium deficiency. Everything else does not show any symptoms like holes in the leafs or something like that.

As a side story I tried to disconnect the CO2, after about a month everything started dying and the water was not clear any more. I wanted to have less maintenance with trimming but it seems that the plants are either thriving or dying.

Thanks,
David Zaninovic