Can someone explain the math?

[aronson]

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

 

[Greg Watson]

Re: Can someone explain the math?

I can't help it... I am a measurer. [...]Hopefully (in order to better educate me) someone can explain the math behind my NO3 readings.

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.

*****IF***** as a measurer you measured correctly ... then each ml of this solution should give you an additional 0.6 ppm in a 29 gallon tank ...

So your 10 ml should have added an additional 5 ppm to your tank ...

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

Mathmatically that's not possible ...

So one or both of two things are true.

1. You have a measuring error somewhere.
2. You have an additional source of Nitrate coming from somewhere.

The additional 16 ppm (plus any uptake) is coming from either your solution or from an alternate Nitrate source. Alternate nitrate sources could be fish food, fish waste, substrate fertilizer tabs ... just a few for example.

However, I would personally double check my test kit/dosing solution first ...

1 ml of your solution should add about 17.33 ppm to one gallon of water ... if it were me, I'd take a gallon of RO water (test it for nitrates to make sure it reads zero) ... then add one ml of your solution, shake it up well, and then test your gallon jug of RO water ... see what your result is ... if it is anywhere close to 17, then you can reasonably assume that both your test kit and dosing solution are ok ...

If this test works out ok ... I'd test your aquarium ... dose some amount of your solution and then test again in 30 minutes or less to see if the reading went up what you mathmatically have calculated it should ... that should eliminate time and outside sources as a source of error ...

[P.S. You can use this jug to top off your tank, so none of it will go to waste]

Does the fish load play some part in this as well?

Not 16 ppm worth ...

Greg

 

[Tom Barr]

Re: Can someone explain the math?

Plants might not be taking up as much NO3 also.

See about adding more CO2, if that checks out, then, check it again

CO2 is 90% of the hobby for folks that use it.
Nothing acts right without it being in a good range.

If you like to measure, measure that.

Regards,
Tom Barr

 

[aronson]

Re: Can someone explain the math?

Plants might not be taking up as much NO3 also.

See about adding more CO2, if that checks out, then, check it again

CO2 is 90% of the hobby for folks that use it.
Nothing acts right without it being in a good range.

If you like to measure, measure that.

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

 

[Ian H]

Re: Can someone explain the math?

If your CO2 is at 34ppm I wouldn't bother trying to raise it further, it is fine.

I also had a 2213 in my 29G tank and added a small powerhead that created nice water movement in the tank without disturbing the surface too much. IMO water circulation is good in a planted tank, it distributes the chemical mix quickly and evenly.

Ian

 

[Tom Barr]

Re: Can someone explain the math?

Probably flow related.

The reactor I designed is better, the vortex and the PG as well as others are knock offs and they seldom use the venturi which kicks the saturation levbekls higher towards the end of the day when you need it as well as purges the O2 out of the reactor.

Regards,
Tom Barr