I would think that would make it hard to check if the stone is getting
clogged, causing backpressure on the pump. Here the water is so hard the
airstones clog and must be replaced regularly.

Hi Carol - what is 'regularly' ? - mine only runs for 3 - 4 months, without
a problem - I have used the same airstone for up to 4 yrs, after I soak it
in bleach to kill the algae, then rinse it thoroughly for next year - if it
will make a whole winter, maybe CLR ?, but at the cost of an airstone, you
only lose 1/2" of airline when you cut the stone off - I am still using the
same airline from 10 yrs ago and have cut 5 or 6 'stones ' off it
Gale :~)