Join Date: Nov 2010
Location: White Plains, MD
I never understood water paramter changes without first knowing what you are starting with. Adding distilled changes water parameters (ph/kh/gh). Not knowing what the values of your water before adding, and further not knowing what the changed values are, can be dangerous to certain species of inverts and fish. Probably hasn't affected anything you have, but not all species may not adapt as well with mucking with things that you may have no need to muck with.
You need to start with measured ph from your tap, gassed off for at least 24hrs, and then gh/kh measured from your tap. From there decide what you need to do in your tank with a desired goal. Without a measured gh from your tap how do you know if you really need calcium/magnesium? If you are going to add those, at least know how much you are increasing the gh by doing so first. You are right that plants need the calcium, but calcium is needed by your fish and inverts as well. Not saying you don't need per se, but I think you need to step back and test and learn what you're staring with and what you have after.
I assume with everything you add to your tank that you perform 50% weekly changes? You can still do 50% even while slowly adding less and less distilled to get it all back to "normal".