Inch per gallon is a good rule of thumb but it's no the say all end all! My LFS
is the same way.
But at the lfs
, they told me I'd be cycled in three days, or when ever the water cleared up! And I could put 6 tiger barbs in my 20 tall just fine, and that a Chinese algae eater could go in a the same 20 tall. But best of all "yep, that common pleco there will be way to big for your tank in a few months, so when that happens come give us back that one and buy another small one, and again after and after they and...."