right i have to be quick as im trying to battle this. i have a 5 ft aquarium which is about 400 litres i have 2 fx5s and 2 hydor 2s. yesterday we bought a 2nd hand fx5 with veconton uv sterilizer both came from a really dirty unwel tank. we i got home i gave them a good wash in side the fx5 the media pipes everything. i wake up this morning to find floating gasping fish i have checked the ammonia and its really high ( the highest one my test can read) at this very moment i am doing a water change what else can i do to prevent it killing any more of my fish. im at college all day and mum and dad are at work. will aquarium salt help ? please help