If you can't afford or don't want to buy a test kit (I know they are quite expensive, even though you get a lot) why not take a water sample to your lfs. Most will do a test for you. Be sure to take a pen and paper to get down the exact values, them saying "it's fine" is usually no good! If you get them, then post them we can take it from there.
According to a booklet I have (from an Interpet med, it has an esay to use table!), gasping near the surface is a symptom of:
Possibe Symptoms:
* Whitespot/ich - other symptoms of whitespot include salt like grains on the body and flicking/rubbing against things
* Velvet - other symptoms include flicking/rubbing, rapid gill movement, red irritated areas of skin, opaque (white/grey) areas of slime, dusting of yellow/gold (1mm) spots giving a velvel appearence
* Slime disease - Same as above
* Higher form parasite - come with large easily seen attachments to the fish (this is unlikely as I am sure you would have noticed them)
Definite Symptoms:
* Bacterial Gill Disease - different symptoms including darkening of the skin, pop- eye (dropsy sign) depending on how acute the disease is
* Poisoning/water quality problems - ie low/high ph, amonia/nirtIte levels, untreated tap water (not using a dechloringator), overdose of medications, household toxins (eg polish, perfume etc)
I don't think you can do anything more until you determine your water parameters.
HTH