CFC said:
If your tapwater has a lower nitrate level than your tank and water changes do not lower the nitrate levels then your tank is over stocked, thats it put simply.
The inch per gallon rule is only a rough rule of thumb for keeping standard community fish, once you start stocking fish like angels the rule goes out of the window and its down to common sence,
hmmmm...
thats interesting
i only use it as a rough rule aswell and since i have tons of experience and knowledge about the species i have in my tanks and their needs, i thought that i could make it thus far without a problem
i only produced the exact inches and calculations at another members request and i am continuously told that is not correct
the rest of my water quality is perfect
so far so good
the nitrates were kinda a shock to me since i take such good care of my tanks
but now i am learning that it is not something to panic over
i thought it was much more serious then it really is
but i will increase water changes (to 30% as said before)
its just a little confusing that 15.5" (even if it IS only 18 gallons once you subtract substrate and ornaments) is overstocked
i understand why but i would not have thought that any of my fish would produce such large amounts of waste
not even the angel due to their slim build and dainty appetite
but live and learn
as i have already said i am purchasing a 55 gallon set-up
and before anything is said (since it always is

) i realize i have somewhat large fish for a 20gallon setup (in the semi-agressive tank aswell as the angel)
that is why i mentioned the 55gallon
is i can keep the tanks running well then i will be just fine until then