I agree with those recommending only significant regular water changes for the present. More than once I have noticed something just not quite right, and before guessing on "treatment chemicals" I do a major 70-75% water change--it is remarkable (well, not really when you consider the benefit of such a W/C) how this solves whatever it was. Provided the GH and pH and temperature between tap (fresh) and tank water is reasonably the same, a large change can do no harm, only benefit.
Second, back in an earlier post the chemical
StressCoat was mentioned. Do not use this. It contains aloe vera, and studies have now determined that this does likely impact the gills and other internal organs of fish. I have never seen any evidence it does what it claims anyway. The fewer chemicals into the water, the fewer into the fish and this is always beneficial. Here's the section on aloe vera from the scientific study:
Water additives that form a protective ‘‘slime layer’’ will contain a polymer (often PVP or carboxymethyl cellulose [CMC]) or colloid (Table 2). Some additives contain aloe extract from leaves of the Aloe vera plant. Manufacturers of these products claim that the Aloe vera extract promotes healing of damaged tissue. One potential drawback to water additives that contain Aloe vera extract or CMC is the addition of organic waste load that can reduce the water quality and oxygen levels in a closed system. This may not be an issue, depending on the density of fish, length of time fish are held, and oxygen content of the water. However, the effects of these substances on gill tissue are unclear. Taiwo et al. (2005) tested the survival and behavior of tilapia (Oreochromis niloticus) exposed to different concentrations of aqueous extract of A. vera for up to 96 h. One hundred percent of tilapia exposed to 50 ppm A. vera died within the duration of the experiment. Fish used in this experiment exhibited severe depigmentation and destruction of organs (including gills). The evidence of the toxic effects of A. vera on fish solidifies the need to empirically test water conditioners, and their chemical components, for potential negative effects on fish.
You will be better with a conditioner that only does what is needed for your water. If this is just chlorine and/or chloramine, the best product I have found is API's
Tap Water Conditioner; it deals with chlorine, chloramine and heavy metals, nothing else. And it is very condensed so less is needed, another benefit for fish.