http://forum.aqua-fish.net/ A forum devoted to aquarium fish, plants, techniques and fish keeping as a whole. en http://forum.aqua-fish.net/?topic=kh-amp-ph-#1 PH needs to be as stable as possible in your aquarium ,so what can cause this to change.The biggest culprit of PH swings is when the KH(carbonate hardness) in the water is allowed to drop to such a low level that the free hydrogen ions start to reduce the PH dramatically. This will drastically affect the health of your fish ,symptoms can be reddening of the gills as they start to literally burn,disorientation on the swimming patterns KH must nevr be allow to drop below 4,if it does start to drop then additives can be used to bring it back to the correct levels.I( found that bicarbonate of soda is the easiest to use but this must be added slowly as any major water parameter change should be avoided mickey 2008-05-06