# Freshwater Aquariums > New To the Hobby ? >  Fish health and water quality

## Sparkie

Hi, I have recently purchased a juwel vision 180 with an internal filter. After a week I started stocking it with a few fish (mollies and platys)only losing one. Since then I have introduced some neons, clown loaches, guppies, pearl gourami and harlequins. I bought 4 guppies and only have one left a fortnight on. Today I came home and all looked well, within 5 minutes the male gourami was dead. He always seemed to live at the top of the tank never really venturing down much. I went straight out and got a water sample and it showed all levels were fine apart from the Nitrite which was a bit high. Could this be what killed the fish or is it just beiginners unluckiness. Also the top sponge (the white cotton wool one) in the filter is becoming filthy after just a day or so (it just looks really dirty). Am I doing something wrong or is this normal. I am worried we are doing something wrong without knowing it, but have read loads of forums and books and can't find anything untowards.
Many thanks.

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