API Stress Coat contains" aloe (Aloe barbadensis
), a chlorine and chloramine neutralizer, and water. API's Material Safety Data Sheet (MSDS) doesn't list the specific ingredient that's used to neutralize chlorine and chloramines, but it's likely to be sodium thiosulfate (Na2
As Fishehgobloop said, API Stress Coat is a water conditioner. It's used to treat your tank water, and should be used according to the instructions on the label.
On the other hand, Melafix is a medication.* (The active ingredient is listed as cajeput oil.) If you choose to use it, you'd add it to previously conditioned water.
There shouldn't be any issue with adding the medication to the treated water. The Stress Coat's ingredients (aloe, sodium thiosulfate and water) won't "interact" with the ingredients in Melafix (cajeput oil).
1) API Stress Coat MSDS: http://www.apifishcare.com/products/msdss.aspx
2) Aquarium Wiki which says API Stress Coat uses sodium thiosulfate, and provides a reference to their source: http://www.theaquariumwiki.com/Water_conditioners
3) Melafix MSDS: http://cms.marsfishcare.com/files/ms...fix_111909.pdf