Managing living systems usually goes better when our methods imitate
nature's. Here's an example of what happens when we don't.

People who keep tropical fish in home aquariums are informed that to
avoid numerous fish diseases they must maintain sterile conditions.
Whenever the fish become ill or begin dying, the hobbyist is advised
to put antibiotics or mild antiseptics into the tank, killing off
most forms of microlife. But nature is not sterile. Nature is
healthy.

Like many an apartment dweller, in my twenties I raised tropical
fish and grew house plants just to have some life around. The plants
did fine; I guess I've always had a green thumb. But growing tired
of dying fish and bacterial blooms clouding the water, I reasoned
that none of the fish I had seen in nature were diseased and their
water was usually quite clear. Perhaps the problem was that my
aquarium had an overly simplified ecology and my fish were being fed
processed, dead food when in nature the ecology was highly complex
and the fish were eating living things. So I bravely attempted the
most radical thing I could think of; I went to the country, found a
small pond and from it brought home a quart of bottom muck and pond
water that I dumped into my own aquarium. Instead of introducing
countless diseases and wiping out my fish, I actually had introduced
countless living things that began multiplying rapidly. The water
soon became crystal clear. Soon the fish were refusing to eat the
scientifically formulated food flakes I was supplying. The profuse
variety of little critters now living in the tank's gravel ate it