hello corsa,
pheew.... where to start.... i don't know what fish you have, so recommendations are difficult. the measures are important for your fish as every fish has certain
ph/
gh/
kh levels where it feels ok. the bad news is that the test you have (a small stripe you hold into the water, right?) is not at all precise. and it doesn't measure ammonia itself at all
no2 should always, always be 0, it is toxic in the smallest concentrations.
no3 can be up to 10, some say 20. it's a nutricient for plants, so that "always 0" might cause plant growth problems. but it won't cause problems for the fish as long as it stays, (to be on the safe side) lower than 40.
PH measures acidity of the water. in freshwater tanks, you generally have levels of about 6-8. lower levels means more acid water, 8 is rather basic (is that the word?).
evidently, if you want to keep fish that are not comfortable with your tap water values, you have to treat your water.
most aquarists would get information about the fish they want keep in advance -
kh/
gh/
ph levels they like, what's the extreme etc. also, it is interesting for breeding purposes since the ranges of values tolerated might become smaller.
no2 and
no3 levels are important to understand if your biological cycle works correctly. that is: fish and plant waste produce ammonia (
nh3/
nh4). then, one kind of bacteria eats away the
nh3/4 and produces
no2 from it. another bacteria, building up its population only after the
no2 is PRESENT in the tank will eat away the
no2 and make
no3 out of it (that means, in that stage the fish, if present, will get problems, until the bacteria population is big enough to deal with all the
no2!!). so
no3 after a while accumulates, since not all of it will be taken up by plants. so
no3 is kind of the end of the circle.
what also matters.... how long has your tank been running? you might be in the initial phase where the bacteria population starts to grow.
no2 is toxic=DEADLY to your fish. if your levels are too high, you can only try to get in extra (bought) bacteria, or filter mud from another aquarist, AND do lots of water changes to keep it down.
so.... more info, betters answers:
tank runs how long?
what fish in it? (latin names are easier for me - as english is not my first language)
what tap water do you have?
kind regards,
silvia