You are very wrong thinking that Sun and a light bulb work
in simillar fashion :-) This example tells me something
important about you... but I am going to keep it for myself :-)

Tell me one thing - what was the reason for you to post
here your message about "some tank", "somewhere out there",
with "some fish" running without water change for "some time" ? :-))
That kind of info is worthless. My tank is also running without
a water change for "some time" and I do not even have
a special secret filter worth patenting :-)) Also, I have
only 4 species of fish, but I am not telling how many
individuals of each species :-)) Experienced aquarist
would easily guess that most species need to be kept
in signles in an average tank but there are exeptions :-)
I think it will be something about 2 weeks now without
even single water change!!! :-))) How impressive!

So - summing up, you are telling here NOTHING worth
considering because it is quite normal for any tank to work
without water change for "some time" with "some fish" in it... :-)

Good luck for you in the patent office! :-))))