do you use it when you do water changes to help contain harmful things?
I use Prime when doing every water change. Des Moines does use chloramine, which is made up a chlorine and ammonia. When a dechlor acts on chloramine, it breaks the bond between the chlorine and ammonia. The chlorine becomes a gas which quickly dissapates into the air, and the ammonia is left behind as a liquid in the water.
Speaking of Des Moines water (this may apply to other areas of the country and world), this time of year the nitrate level of tap water goes up. I keep a log of water tests and every 10 days or so I test my tap water too. I've been geting between 10 and 20 nitrates recently. This is common when ferts from farming are washed off the fields by rain.
is the botanical oils or aloe vera bad in any way?
I don't think it would be harmful, but I don't like the residue it puts on some types of plants. I've used Prime for years, back when I kept reef aquariums, have never had any problems with it, so continue to use it.
"If it ain't broke, don't fix it." is what I go by. HAHA!