# Help me calculate my ppm, please ?



## ian_m (20 May 2013)

Had a timer failure last week and ended up empting 1litre of 1.5 strength EI Macro mix (from Aquarium Plant Food) into my 180litre tank. Not 100% sure what happened, but left the remote control for my timers away from the tank which managed to turned air on, lights off, ferts pump on but not ferts pump off. .

The next morning my wife could hear a whirring under the tank. It was the macro peristaltic pump still whirring on an empty container (whoops....).

Fish didn't seem to mind, more concerned when I was looking to "are we going to be compensated for this, with a bonus feed". Did a 75% odd water change (at 7:15 am ) and everything appears OK. Plants might be smiling? Tetra test strip kit, first time I have used them, indicated NO3 between 100ppm and 250ppm.

Parameters would have been 12tsp Potassium Nitrate, 3tsp Potassium Phosphate & 18tsp Magnesium Sulphate into 180litres of water.


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## dw1305 (20 May 2013)

Hi all,
The easy way is the dosing calculator at "James' Planted Tank" <James' Planted Tank - Dosing Calculator>. This gives 245ppm NO3 for "12 teaspoons" KNO3 in 180 litres dosed at 1000ml, and 204ppm for 60g KNO3.

If you want to check, you need to convert tsp to grams (approximate) at 5g per teaspoon.
So that gives 60g KNO3, 15g KH2PO4 and 90g MgSO4.7H2O

You then need to work out the % of each element in each compound, using the RAM/RMM.
K RAM = 39.1, N= 14, O = 16 = 39.1 + 14 + (16*3) = RMM = 101.1, so approx, 39%K & 14%N.

To get a ppm in the tank water you need this formula:
So for N from KNO3:
 (wt compound x 1000) x % element = 60 x 1000 x 14 = 47ppm N
.........dilution ........................100 ..............80.........100

Then to convert N to NO3, you need to calculate the % of N in NO3 (14+48 = 62= 22.5% N), so:
47/0.225 ~ 210ppm NO3.

So somewhere in between 200 - 250ppm NO3 added, and we believe in "James' Calculator".

cheers Darrel


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## ian_m (20 May 2013)

Hurrah, for once a test strip was right. Take the Ceg...

Shame the LFS think that any NO3 above 50ppm is fatal for fish and that I should buy some really expensive "nitrate away" solution and matchingly expensive "nitrate filter foam" for my filter.....but we know different.

I wasn't too worried (apart from cost of 1litre of EI solution) as a quick "in the morning" calculation by me (assuming 6gr per tsp) came up with 250-300ppm NO3.


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## sciencefiction (21 May 2013)

That depends on the types of fish, and also how long they are exposed to those amounts of minerals. I doubt it NO3 in hundreds is lethal to most fish but it may not be perfectly healthy long term either. Your plants will take care of that I suppose


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## dw1305 (21 May 2013)

Hi all,


ian_m said:


> Hurrah, for once a test strip was right


You've got much more chance of getting a "ball-park" figure with large concentration of NO3- ions, because this reduces the relative concentration of other anions, particularly chloride Cl-, which will interfere with the reading. It would be interesting to do the test again, but this time add some salt (NaCl) to the water in the test container.


ian_m said:


> Shame the LFS think that any NO3 above 50ppm is fatal for fish.


They do have a point, if you haven't added any nitrate ions (either directly through KNO3 etc, or indirectly through your tap water supply), the nitrate is the "smoking gun" from the conversion of ammonia. The difficulty is convincing people that both high nitrate levels and fish death are products of the ammonia, not cause and effect.


ian_m said:


> and that I should buy some really expensive "nitrate away" solution and matchingly expensive "nitrate filter foam" for my filter....


Back to "magic bullets", there is no money in telling people that they need plants to remove their nitrate, but if you can sell them an ion exchange sponge or resin.........


sciencefiction said:


> I doubt it NO3 in hundreds is lethal to most fish but it may not be perfectly healthy long term either. Your plants will take care of that I suppose


There are figures from re-circulating systems aquaculture, this one looks at the sub-lethal effects of 200ppm NO3- on "Hybrid Striped Bass":  <http://www.atlantech.ca/public/articles/Water%20Quality.PDF>.
Some fish are very tolerant to short exposure to high NO3 levels, Channel Catfish (_Ictalurus punctatus_) and Tilapia (_Oreochromis_ spp.) for example. This is from: <http://www.crc.govt.nz/publications/Reports/report-review-nitrate-toxicity-freshwater-aquatic-species-000609-web.pdf>


> The acute toxicity of un-ionized ammonia, nitrite, and nitrate to 50–76-mm fingerling channel catfish (_Ictalurus punctatus_) was investigated using a static bioassay system at 22, 26 and 30°C. The 96-h LC50 values at 30°C for un-ionized ammonia, nitrite, and nitrate were 3.8, 44, and 6,200 mg/l.


 I couldn't find the figures for Tilapia, but I seem to remember that the LC50 number was even larger.

cheers Darrel


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