Bobtastic said:
..I was wondering if there was any reason not to use regular tap water in our EI mixes? Atm I'm using deionised water in my mix as it was called for in a DIY TPN+ mix...
Hi Bob,
No there is no reason.
JamesC is a very precise and organized individual, therefore he does not like the idea of introducing a nutrient level into his mix that is unaccounted for (especially since it cannot reliably be measured). Tap water will also introduce uncontrolled levels of other ions such as Calcium, Magnesium and Carbonates/Bi-Carbonates, so if you were running a soft water tank and were concerned about TDS then using RO/deionized would minimize the TDS increase in the tank. Someone like Ed Seeley would use this method because he specializes in breeding soft water fish.
JamesC's goal when developing DIY TPN+ was to simulate, as accurately as possible, the NPK and trace concentration values of the commercial TPN+. In this way it would be possible to predict performance, and to compare performances more accurately and more consistently than if an uncontrolled and unknown nutrient level were present in the mix. This is a scientific and highly rational approach, but for most users this is also completely irrelevant. Since it is not your purpose to study effects or to compare performance factors you should not care what kind of water is being used, unless your tap water contains significant levels of known toxins such as herbicides.
Your goal is to provide at least the minimum nutrient value necessary to avoid nutrient deficiency. If this is your objective then it does not matter if your mix has inconsistent nutrient levels from batch to batch, or whether your mix has a higher or lower nutrient level than the batch made up by the boy across the street. If both of you added the same ratio of powders to water then you are assured that both mixes contain at least the minimum required nutrient level. That is all EI cares about. Do not make things more complicated than you need to. This is why we have difficulties, because we pay far too much attention to things that do not matter while ignoring the things that matter most.
Therefore, use whatever water you want, whatever is cheapest or whatever makes you happy, whether that be RO water, tap water, Antarctic iceberg water, or even ancient Babylonian water pilfered from the Museum of Natural History. But just don't worry about it because it will not make any difference. If you have trouble with fungal growth then just add a few drops every now and then of any strong acid such as Muriatic or Sulfuric. That will prevent fungal growth.
Cheers,