First, i doubt that the PH would have much if anything to do with gasping. Often times gasping is a result of a lack of oxygen saturation. Contrary to popular belief airstone themselves to not add oxygen to the water, the agitation of the surface and the current flow cause by the air bubbles rising to the surface and breaking is what adds aeration.
If you have a lack of filtration and surface area you will have a lack of oxygenated water. In most small tanks a simple air stone will take care of the problem by providing water circulation and surface agitation. In much larger tanks you might need to increase your filtration with something like a larger HOB filter or canister filter. I am going to guess this is a small tank maybe 10 us gallons. that being said try an airstone first.
this may not solve the problem. You may have an issue with dissolved solids. A much more important factor than PH but related. A simple and solid way to reduce the dissolved solids and effectively reduce the PH is to add peat to your filter. The peat will absorb the dissolved solids and reduce the PH. Do some research on the subject before going ahead with it because toying with your disolved solids can result in dehydrating your fish. Here is a document to help start your research. hope all of this helps.
http
/hjem.get2net.dk/Best_of_the_Web/TDS.html
To address the water changes, it is not a bad idea to perform regular weekly 25% water changes on any tank. If your filtration is inadequte you may find the need to increase the water changes. Certain fish such as discus require water changes almost constantly. A water change will assist you in many ways. First, you will be removing organics which cause issues with amonia nitrates and nitrites. By adding new water you will help to replenish the minerals used by your tank from the water itself. You will also be dilhuting the water in a sense, so if you have poor water conditions such as high or low ph, cloudy water, medically treated water, a high buildup or dissolved organics, etc... the water change will help to slowly adjust those to the optimal conditions.
