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=why-is-water-quality-important-#1 Nearly all of fish diseases or illnesses are usually brought on by poor water quality. There is an old saying in this hobby Look after the water and the fish will look after themselves. If the water paramaters are not to a high standard problems will occur. Poor water will shorten the lifespan of your fish Throwing medication into the water will work short term but if the quality is poor the problem will come back. This is why tanks need cycling,ammonia is lethal to fish,nitrite is not so toxic but it can react with the fishes blood reducing its ability to absorb oxygen.It will weaken the immune system. Nitrates,even less toxic can still cause problems to fish if at too high a level.Water changes will reduce the nitrates but remember. doing a 25% water change will not remove 25% of the nitrates,only continual water changes will have any effect. Nitrates and phosphates will promote algal growth, it has the opposite effect on fish - it will stunt their growth. Testing your water on a regular basis is a must to ensure your fishkeeping habits are working. mickey 2008-05-29