Actually, you need to find out WHAT makes up those initial tap water PPM's in all honestly. Some things that will be detected by the meter is NOT even plant food at all, or it can be in a form that is not available to the plants and will not effect them.
This is especially true for organic compounds but NOT limited to organic sources only. Most all organic compounds for example are toxic to the plant until they are converted by microbes into something the plants can use.
If you just count the 300PPM's blindly so to speak, you could come up short on certain elements, OR much worse you could be adding to much of "something" causing a lockout problem.
You for sure need to "count" those 300 PPM's if it is coming from something that is used by the plant, like calcium or magnesium which is usually what is found in tap water in various forms and concentration levels....there is a HUGE difference in the types/forms like a "carbonate" verses a "bicarbonate" which is one of many examples.
This is why it is a must to get your tap water sample looked at by a lab for analysis. THEN you can begin to build a proper "nutrient profile" and all the guessing is removed from scenario.
I do not understand why more people do not have this test done as the money you spend on the sample testing is far less than you wasting time and nutrients and water and money "guessing" or using the "trial & error" method trying to either figure out what is missing or what there is not enough of........for me damn near any price would be worth the piece of mind and knowing that the plants that are so important and valuable are in the BEST possible conditions so the BEST possible outcome is achieved. No waste.
In some cases depending on where you live and where your water source is coming from or managed by (local "city" water company for example), you can get the needed information or at least most of it from the water company websites, or by calling the water company or whatever the source is for your water.
With "well water" being the source, IMHO this water sample testing is almost a MUST without exception as the "well water" can and usually does in fact, contain some serious levels and concentrations of minerals, ect....
With well water, the information should already be available from the initial drilling procedure but re-testing is still suggested as the environment is constantly changing, especially with the added popularity of propane gas drilling which is known to contaminate the water table with all sorts of NASTY ASS SHIT. There is a documentary on this ongoing and rising issue on HBO called "Gas Land".
But anyhow the point is that the data should be already available as when the water well was drilled or "tapped" initially, they should have ran test for analysis which is common procedure when drilling water wells. Getting periodic samples tested (twice a year) of your well water is a very wise plan IMVHO.
Be Well
HR
