DOCs?---what are these?

[Hallyx]

Ammonia is eliminated by a three stage cycling process involving nitrifying bacteria. But, even in a cycled tank, we change the water at least weekly to restore minerals and to reduce DOCs (dissolved organic compounds) which are not converted nor trapped in the filter.

So what, exactly, are these DOCs? And how do they effect our fish?

[Bettafish]

I think they work in that they Get into the fish through the gills or food. And they draw out minerals or liquids that the fish need. like water.

I think ammonia is in example. its technically an organic chompound and it is dissolved in the water. and if theres enough then it harms the fish.

So probably some heavy metals or... heck i dont know whats really in the water :/ probably something bacterial?

can i have some help on this?