personally i would suggest getting a bigger tank ASAP. 50 litres is next to nothing,second hand 100L+ tanks are cheap as chips inclusive of stands etc on ebay and ur bound to have one local to u (check ebay and gumtree etc) and im sure u have a couple of square feet free in ur tank room to have a proper tank (I went from a 17L tank to a 90L tank then to a 240L tank in the space of 6 months)
Tiny tanks either make for cruel set-ups or having only a couple of fish in them