Biorb 30ltr tank - water is always cloudy despite changeing filter etc - WHy?

how do you clean the filter out?you re supposed to wash it in the tank water.i have 3 biorbs and 1 of them kept getting cloudy.i have 2 with tropical fish in and 1 with goldfish in.it is big enough for goldfish so take no notice.the one i have 4 goldfish in is a 30ltr and they have plenty of room an the other 2 biorbs are 60ltr.the one with the goldfish in gets dirty alot quicker than the tropical tanks as goldfish pooh alot more than tropical fish do.you need to buy another tank for the neon as it is tropical.just do a 50% water change every other day till it goes clear.if you have just set it up you may have new tank syndrome.just clean your filter properly and clean out the tank.ask your local aquatics shop if they have anything for it.once it goes clear ou will have to keep on top of it.i clean my goldfish out every week as they pooh for britan.also are you putting any water treatment in there when you clean them out as it puts in some goodness and takes all the stuff out of the water thats harmful to the fish,if not also speak to your local shop and ask for some of that.hope this helps and good luck.