# London Tap Water, EI and Magnesium



## greenink (2 Aug 2011)

Am confused about whether I need to add Magnesium Sulphate to an EI dose if I live in London.

Thames Water's quality report for my area is here. They give a minimum of 18.9 ppm of Nitrate NO3, but nothing I can see for Potassium K or Magnesium Mg.

Judging by this, it seems I could cut the NO3 dose in my EI calculation considerably. Is this right?

I've also read that hard water has a high concentration of Magnesium. Since this is very hard water (CaCO3 is 285 ppm), is the Magnesium also likely to be high enough not to dose Magnesium Sulphate in the mix? What level should I dose this at?

Does anyone know?


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## ceg4048 (2 Aug 2011)

Hi Mike,
               I strongly advise to banish any thoughts of lowering NPK values until the tank itself proves to you that lowering the dosage is acceptable. When it comes to NPK the municipal water report means absolutely nothing unless the workers in white lab coats took their sample directly from your tap.

When it come to micronutrients we can be a little bit more lenient, however, unless the specific Mg value is listed then you have no idea whatsoever how much Mg you actually have. the CaCO3 value of 285 tells you nothing about how much Magnesium is in the water. It could be high, medium or even zero. Again, because Mg is one of the more critical elements it is not a good idea to just assume that everything is OK. 

Unless you intend to breed softwater fish I see no reason whatsoever to be in a rush to reduce nutrient dosing. You should ignore the water report, dose the baseline values and see how the tank responds. Then you can make the adjustments from there. Only The Matrix teaches us to employ low nutrient values as a default assumption. Those of us in The Real World know that it always better to start high and to reduce the dosing as required. This is a much easier path to success.

Cheers,


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## greenink (2 Aug 2011)

Thanks - much appreciated. Was surprised quite a lot by the variance in the tap water samples they measure: NO3 is triple the amount in some samples....

Am going with your doses - will track progress in the journal. (And thanks for writing the original articles and various posts in such a clear way - they've certainly helped me a lot).


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## greenink (9 Aug 2011)

For anyone interested in the K and Mg levels in Thames Water, they've just got back to me:

"Potassium and magnesium are not regulatory parameters i.e our water quality regulator (Drinking Water Inspectorate) do not require us to check the levels of these, so there are not much data to check.  However, there are some historic operational sample results from the supplying water treatment works (and concentrations are unlikely to change in distribution).

Potassium concentration (in parts per million): minimum= 4.6, average= 6.6

Magnesium concentration (in parts per million): minimum= 5.0, average= 5.5

2) Minimum iron for the area is less than 1 part per billion, average iron is 6.3 parts per billion."

So in theory could cut back on the Mg Sulphate quite a bit in the EI regime. But perhaps not yet.....


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