I currently have a 4' tank which houses a 6" oscar. Filtration is a Tetratec EX1200 external filter. The tanlk has been running well, and I recently cleaned part of the filter medium in tank water for the first time. The only thing that worries me is that the plastic pipes leading to and from the tank are starting to get a little mucky - is this normal or should they be replaced periodically? Otherwise I have no real problems and a happy /clean oscar! 