Generally you want to avoid using chemicals to cover up problems, but in an emergency situation it's okay. We try to stress that chemicals do not replace the need for water changes, and that they are generally unnecessary (i.e. a waste of money).
Also remember that when you put chemicals in the water you are contributing to the osmotic pressure in your tank. A simplified explanation for this is... Water and chemicals in it try to equalize themselves between membranes...if there is more chemicals in the water than in the fishes body, water will try to leave the fishes body to equalize the amounts. The more chemicals, the harder the fishes body has to work to keep the proper balance within itself. Osmotic pressure is one of the reasons true saltwater fish cannot live in freshwater and why true freshwater fish cannot live in saltwater.
It's also really difficult to tell how long those chemicals keep toxic ammonia in it's less toxic form. In lower pH water (under ph 7) ammonia is more likely to stay in it's non-toxic form, while in higher pH water (over ph 7) ammonia is more likely to be in it's toxic form.
Sorry, not trying to drown you in science. Basically, use the chems if you think it's necessary, and do a big water change at the next opportunity. Remember that even if it's locked in the non-toxic form, the Ammonia will still be visible on the test. Once you get the ammonia down to a safer level, if you feed sparingly you should hopefully be able to do smaller, more manageable water changes (although they still may have to be done daily).
