Can someone explain the math?

After some research on these forums and help from it's members I am now dosing and water changing with wonderful results! Thank you to everyone! Thank you to Tom for hosting such a great resource.

I can't help it... I am a measurer. Maybe it comes from my other hobby; woodworking but since receiving my Lamotte Nitrate testing kit I feel empowered. With that said I have been wondering about the results of my test kit over the past few days. Hopefully (in order to better educate me) someone can explain the math behind my NO3 readings.

First, the particulars about my tank:

29g, 130W CF @ 6700K for 12 hours/day, CO2 w/SMS122 and Regulator, Eheim 2213, PH: 6.9, KH: 9, GH: 17. Heavy fish load: ~20 fish and 5 shrimp and medium plant load (I think).

My tap is pH 7.1 and NO3: 6.6. I am not sure of the K or PO4 (my PO4 test kit has yet to arrive).

On July 7th I did a 80% water change afterwhich my Nitrate kit showed 8.8ppm. I then dosed 10ml of KNO3 using a solution that has 15g of KNO3 in 140ml of RO water.

This morning (2 days later) the NO3 measured 30.8ppm (!). I then did a 60% water change (I am fighting a low level ich problem) which brought the reading down to 15.4ppm. Needless to say when I added ferts after the water change I did no add KNO3.

So why did the uptake not reduce the KNO3 I dosed on the 7th? Or, am I adding too much and it did reduce it down to the 30.8? Does the fish load play some part in this as well?

Details of my dosing regimen can be seen here if anyone is interested.

As always, thanks in advance...

Adam

 

Re: Can someone explain the math?

Tom (and Greg),

Thanks for your responses! I am going to check my solutions as per Greg's suggestion as well.

As opposed to measuring... is it safe to assume that at a KH of 9 and the SMS showing a pH of 6.9 I can determine my CO2 to be 34ppm? If so, can/should I push it much higher than that?

I have found that it is difficult to push my CO2 below 6.9. Exponentially so it would seem -- my water doesn't seem to want to absorb the gas in my vortex after the pH hits 6.9. I've tried to get it to 6.8 but haven't been all that successful.

Also, could it be that the water volume is not moving enough? There is very little movement in the tank outside the flow of my Eheim and any currents produced under the vortex.

Thanks again for your help!

Adam