First, you should only use a conditioner that deals with what you need for your particular tap water. Dechlorinators, like any substance added to the aquarium water, will get inside the fish, in their bloodstream and internal organs, either via osmosis through the cells or via the gills. The fish have no control over this, it just happens. So you don't want to be adding chemicals that are unnecessary. Sue made this very important point in her post about Prime...it does a lot that most of us do not need; I do not like the sound of something that messes around with the bacteria/nitrification processes, especially when the manufacturer admits they themselves do not fully understand how it does this. Also, these products add TDS (total dissolved solids) to the water, and these also get inside the fish, and soft water fish in particular have real issues with TDS.
Second, avoid conditioners that include questionable (if not dangerous) additives, like the aloe vera. A scientifically-minded friend of mine yesterday sent me a link to yet another study on aloe vera. Suffice it to say, this stuff has no benefits long-term and is now believed to be detrimental to fish gills. Another substance added to the Nutrafin (Akasha, you mentioned this brand in post #1) is valerian. I used to use this conditioner until someone pointed this out. There is absolutely no benefit to dumping valerian in a fish tank..why would one need to drug the fish to sleep? So read labels carefully.
I am using API Tap Water Conditioner. It deals with chlorine and chloramine (if you have just chlorine, like I do, you can use even less per dose, this is common with most conditioners) and heavy metals, but nothing more. There are conditioners that do not detoxify heavy metals, but having tried them they have other issues so I will leave that topic. I do not know the product fluttermoth mentions, it is not available in Canada (so far as I know), but from what I could see in her link it should be OK unless you can find it has something else in it.
Last comment...notwithstanding that pretty much every manufacturer of conditioners says you cannot overdose, or not harmful if overdosed, this is absolutely false. I think I made clear why in the first point above.
Byron.