Hi, I would like to get an external filter for my Rio 180L but don't have much money. I hve been looking on ebay and the prices are less intimidating. What do I need to look out for if buying wierd makes or 2nd hand? Is it a mistake to do this? I don't want to come home and find that the livingroom has becaome a marsh and all my fish are dead. Also if they are really rubbish and I'd be better saving my money up and waiting I would like to know. Any experience/warnings or tips for spotting a good one appreciated.