Len,
I would not trust the N test kit. If the P is dropping, you likely have enough NO3.
Plants will take up some PO4 even at low NO3, but not for long.
Just keep adding KNO3, traces and the CO2. I suggested some other things like better current and mixing etc. Try those also. Mixing becomes harder in larger tanks.
You have only a fewe variables to monkey with.
Light
CO2
KNO3-generally do not trust your cheap kits
KH2PO4
Maybe some GH builder, SeaChem EQ etc
Traces.
I have not been fond of CMS, I'll alternate days that I use it with Flourish.
I like TMG a lot also.
Might give those a try and give it 3-4 weeks to see.
Other things are maintenance routines.
But the basic notion is still not allowing the plants to run out of any nutrient. So adding more than what you suspect with test kits is often warranted and should not hurt the tank(you already have some issues but as long as CO2 is good, these should not harm anything).
So adding a little more will tell you if that is the correct path or not.
Note the plant's health, nothing else like algae etc.
Regards,
Tom Barr
I would not trust the N test kit. If the P is dropping, you likely have enough NO3.
Plants will take up some PO4 even at low NO3, but not for long.
Just keep adding KNO3, traces and the CO2. I suggested some other things like better current and mixing etc. Try those also. Mixing becomes harder in larger tanks.
You have only a fewe variables to monkey with.
Light
CO2
KNO3-generally do not trust your cheap kits
KH2PO4
Maybe some GH builder, SeaChem EQ etc
Traces.
I have not been fond of CMS, I'll alternate days that I use it with Flourish.
I like TMG a lot also.
Might give those a try and give it 3-4 weeks to see.
Other things are maintenance routines.
But the basic notion is still not allowing the plants to run out of any nutrient. So adding more than what you suspect with test kits is often warranted and should not hurt the tank(you already have some issues but as long as CO2 is good, these should not harm anything).
So adding a little more will tell you if that is the correct path or not.
Note the plant's health, nothing else like algae etc.
Regards,
Tom Barr