Hi chriso and Welcome to TFF!
Excellent question that puts you right into an important topic here in our section! In fact, contrary to what many of think as beginners (and may be pushed to think by the folks who want to sell us as many bottles as possible,) tap water is wonderful stuff for tropical fish! It should be assumed that one's tap water is good until proven otherwise!
Tap water contains Calcium, Magnesium and other trace minerals that fish need and that also have probably been constituting the total mineral or "hardness" situation that their cells have been getting used to being balanced with (remember that stuff in school about how cell walls do the job protecting the cell from too much concentration or dilution of substances on the inside versus out, lol?) Often our fish are acclimated to the tap water where we purchase them and it's often the same as ours (though not always of course.)
In a forum peppered with experienced aquarists you will begin to hear lots of stuff about doing fancy things to your water, but as a beginner you should remain cautious. The really experienced ones will tell you to first hope that your tap water is decent for the type of fish you want to keep - this is the best state of affairs possible! It's actually quite a rare thing that one goes to the trouble of "creating" water of a different type (hardness, pH etc.) because it's a huge and trouble-prone undertaking, especially since it can force you into procedures that you have to keep doing week after week, year after year!
Anyway, let us know -why- you are thinking about water other than your tap water. Some of the Nutrafin testing kits are ok (I have a KH one I like) but in general many of us don't like these as much as the API or Salifert kits. Most of us for beginners like and recommend the API Freshwater Master Test Kit.
Your other question about water removal methods falls into a completely different category. While in some situations it would certainly be better to change water than not to even if one did not have a "gravel cleaning siphon" because one were just beginning in the hobby.. it turns out that having and using these "cylinder and hose" contraptions is right at the heart of one of the most important maintenance skills in the hobby!
Using a gravel cleaning siphon (by which we mean a hose with the (usually clear) cylinder attached that allows the gravel to fall back into the tank after being disturbed and sucked up a few inches by the outgoing flow of water) is an extremely important thing, often right from the beginning. It can even be needed a few times during those first couple of months while you are fishless cycling your filter to turn it in to a biofilter. But it really begins to shine (well, I guess we wouldn't think that about brown debris
) once your filter is cycled and you've introduced your first fish! The gravel siphon is the key part of the habit we call the "Weekly Water Change!" I think of it as one of the most powerful habits for beginners to learn.
Even when the water is crystal clear, the tank new and the gravel not even seeming to have debris, it turns out that the gravel siphon can do important work. Many of the nitrates(NO3) and other invisible ions and molecules we want to remove will hang down with the gravel because of gravity or molecular charge and it is only via our "disturbance siphon" that we easily change this situation.
~~waterdrop~~
