Shanunm81,
Aside from the concerns about pathogens in water you collect yourself, also consider the amount of particulate organic carbons (POC’s) in the water that you can or can’t see with the naked eye. Even if you test the water at the source for nutrients such as n03 and P04 (nitrate and phosphate) and it is within limits, consider that they will only raise in time as POC’s decompose into dissolved organic carbons (DOC’s).
For example, you could take a sample of spring water today and it reads 0 for n03 and PO4. Hold that same water in a bucket for a week and test it again and the levels will be higher, sometimes significantly or sometimes trivially depending on POC levels. Not only will these raise measurable nutrients but also nutrients we can’t or don’t measure on a hobbyist level such as glucose, amino acids, carbohydrates, etc. These help fuel algal growth and in excess deteriorate water quality for fish. Similar to how decomposing plant matter fuels algal growth in a planted tank, we try to remove plant detritus to avoid adding DOC’s to the water column.
If you must use spring water, I suggest treating it in some way first. A process of boiling, straining through an extra fine micron sock (culinary or reef aquarium suppliers should have these) and using activated carbon in your filter should minimize risks.