Re: What happens if you overdose on KH2PO4 ?
Folks add 3-5ppm of PO4, others have certainly overdosed KH2PO4, many think it's KNO3 or K2SO4 and start adding 1/2 teaspoons 3 x a week to 55 gal.
Run that through Spar's Calculator
If you uprooted a lot of the tank. if you had a fish die, old filter that needs cleaned, used Jobes sticks in the past, used house plant fertilizers etc.
Sunlight also helps in some tanks with poor CO2.
But few can induce GW without NH4 and anyone can make a broth of pea soup with NH4. I;ve gone to over 100ppm with NO3, and about 3ppm with PO4.
No green water, the difference between 3ppm and 10ppm to the algae is neglible, it way beyond any limitation the plants/algae or any organism might require.
Regards,
Tom Barr