they need to change because the plants die and stay also animals die and stay there with there sickness
they cant change kids lifestyle but they can educated kids on how to keep healthy.
Give it a good home, feed it, and change its water
to keep it clean. ..
chlorine
you can keep your stomach healthy by eating healthy foods
By reading Twilight!!! and exercising. and eating healthy. everything you do to keep your body healthy, will keep the system healthy.
you keep it healthy by pooping on your self
Chlorine.
To let the Sun light in and to keep the rain out. It also stops leaves going into the pools.
Plainly said, to keep the bugs out :)
Silver. oxygen.
chlorine or the filter