[dewalltheway]

My ludwigia plants have been growing great until the last week and something has gone wrong. I looked on Chuck's website for NUTRIENT DEFICIENCIES and it is pointing to low potassium but I have no way to see what the potassium level is in my tank. I have been adding potassium nitrate because my nitrate was at zero and I just tested it and it is at 10ppm which is high for my tank (15 gal). I do water changes every week and have a DIY CO2. I tested my PH and it is at 7.8 and the KH is at 251 ppm which per Chuck's calcs make the CO2 at 7ppm which is low. The phosphates tested somewhere between 5-10 ppm which is way high. I have added pics below and would apprieciate anyone's input. Also to let you know that I am running 3-15watt bulbs for lighting for 12 hrs per day.
Thanks!!

 

[mistergreen]

it could be potassium.. I'd lower the light to 30watts.
seachem sell a potassium you can use.

 

[dewalltheway]

I bought some potassium sulfate from Greg Waston and it should be here in a couple days. I just wish there was a easy and inexpensive way to test for potassium!

 

[IceH2O]

You can't overdose pottasium so it would really be a waste to bother testing it. The best test is sight. If you see you don't have enough then add more till the problem goes away.

KNO3 never adds enough K. Good move getting the K2SO4 ferts from Greg. Use the calc and figure about 20 ppm and wait about a month, the deficiency should disappear, then you can lower it by 5 ppm every 2 weeks or so till you see the deficiency show again. Just up it 5 ppm from that point and you'll be okay. You could probably get away with 1 tsp per week to start off with and just lower it from there.

 

[dewalltheway]

Can you dose to much potassium where it will hurt or kill the fish?