we have a 35 litre tank and each time i put fish in they tend to go belly up i have cleaned it out today using hot soapy water and rinsed it out under the outside garden tap i upgraded my daughters guppys to it and already one has gone belly up i am so confused why this is happening.A while ago my partner brought some chiclids of trade me and the cold water they arrived in smelt so funky im wondering if there is some KILLER bacteria in the tank or what i have changed from using the internal filter that came with the tank to a another filter witch hasnt killed fish
any ideas