looks like an Aqua One 54 litre tank, certainly need to consider your stocking. Try googling all the fish and reading up on how they shoul be kept. Seriosuly Fish have excellent profiles for tropical fish, worth a visit to read up on them all. 1 Tiger barb for example is a poor choice for many reasons. As others have said, read up on cycling, its not a case of just leaving the filter running for weeks on end, doing that will not create "friendly" bacteria in the filter, for bacteria to thrive, it needs a food source. gluck.