Low maintenance tanganykan aquarium

Hi, my tank is only a 20 gallon size,
and I have 5 tanganykan cichlids and 5 red crabs.
I never changed the water, I never syphoon the bottom to clean it,
because I don't feed them very often.
I only add new tap water due to evaporation, but I cover all my
holes, so the evaporation occurs very slowly.

I have not changed water since October of 2000.
I feed my fish , just cichlid flakes, once a month.
I cover my tank with all sides with paper or blanket so
it will not create algae on the walls.
Also under dark conditions, fishes of the cichlid genre,
are less active at night than day.

Everynight when I am home, I just appreciate the beautiful
peaceful and tranquility of colorful tanganykan cichlids
comingling with red crabs.My fishes are not much bigger than
my red crabs of course.