Quick question since I am just starting with K2SO4 and am going away for 2 weeks, giving me no time to experiment myself and observe the results...

I'm switching from EI dosing KNO3 to K2SO4, since my nitrates are fairly high ... usually getting to 50ppm the day of my water change.

My standard EI dose for KNO3 is 1/2 tsp 4 times per week. Since KNO3 is 39% K and K2SO4 is 45% K, I'm figuring I can just substitute 1/2 tsp K2SO4 for the 1/2 tsp KNO3. Sound OK to you all? I guess extra sulfur doesn't hurt anything.

When I get back from being away, I'll make sure my nitrates are not too low or too high still, and make any necessary adjustments. I do have quite a few fish in my tank, so it may come down to more water changes if my nitrates are still too high.

Thanks in advance for any advice you can give.

The obvious advice is to calibrate your nitrate test kit very carefully, using solutions with know amounts of nitrates in them. Otherwise you may not actually have all of the nitrate you think you have. If that is the case you could come back to an aquarium in distress after cutting off the nitrate dosing.

You are wise, Hoppy. I'm not sure I can get those calibration solutions in time, therefore I'll probably go 50-50 KNO3 and K2SO4. I'm actually going to reduce my EI dosing slightly while I'm away because I do not want someone to have to do a full water change in the middle of the 2 weeks -- they are going to do a 10% water change for me, however.

Would those calibration solutions be available at an LFS do you think? I've got time for a quick trip. Or, perhaps the Seachem (or some other brand) Nitrate testing kit has a calibration solution. I'm willing to buy one.

Thanks for the advice.

Just curious but what could you use to make a NO3 calibration kit? I have access to a balance that is pretty spiffy, but I'm not sure how to go about making one?

Just did some research and came up with the following:

1g of KNO3 to 500ml of distilled water = 2000ppm Nitrate solution

Add 12.5ml of this solution to 487.5ml of distilled water and you should have 50ppm Nitrate calibration solution.

Here's a link which should support this (if my and their calculations are correct): verifying Recommended EI dosing.

The only thing is the purity. If there was a way to account for that the solution would be a little more accurate. It would be kinda hard to measure 487.5 mls of water really accurately. How much to add to 1 L?

If you make a 50 ppm solution which is really a 40 ppm or 60 ppm solution, you still have an accurate enough solution to calibrate within the accuracy we need. Use that solution as is for a 50 ppm data point. Mix 10 ml of it with 10 ml of distilled water and you have a 25 ppm data point. Mix another 10 ml of distilled water in that solution and you have about a 15 ppm solution. Etc. That is good enough to avoid thinking you have 50 ppm when you really have 1 ppm.

Okay. So how bout this. I'll add exactly 1gram to 1L to get a 20ppm solution. Then I can mail out 1L of water to you all. I'm not sure on the shipping, maybe 500mls would be better. Or better still, if you all have a means to dillute I can mail out a more concentrated solution for you all to dilute. What about a more concentrated Solution? Say a 500ppm solution to dillute down? Let me know what you think would work best.

I guess I'll just use MQ water and the Aquariumfertilizer.com KNO3, but I'll let you guys know if I see anything that may be a little bit more pure at the lab that has nitrate in it and isn't crazy toxic. The balance is accurate up to the nearest milligram so it should be pretty close. And I'll use an Erlenmeyer flask with and etched 1L mark and try to make it as close as possible.

Also, can I do the same with PO4? We have 99.9% pure Potassium Phosphate at the lab so that won't be a problem. Anything else that you all would need to test against a standard? I guess the NO3 standard could serve as a dual K standard if the nitrate ion doesn't interfere with the testing method. I'm so lazy I'll let y'all do the calculations...Its probably pretty bad that I can't do these without looking them up.

Let me know the numbers and I'll do my best to get it out to you guys. It may be a while though. I have finals coming up soon, but I may be able to find some time. School can be such a downer .

Creighton,

I have a friend with a super-accurate scale, so I can make the calibration solution close enough for my needs, since I do have pipettes and beakers. The cool thing about EI is that you do not have to be perfect ... as the name implies we are just "estimating" and that's good enough in the end. Thank goodness!

Good luck on the finals ... I remember those days well.

Cool beans. What are you waiting for? Make some calibration solutions! But after all it is estimative...


Hopefully I'll pass all my classes. Electrical Engineering 312: Circuits Analysis is HARD!

The offer still stands for those that would like to try some.