Fishes are generally cheap to maintain. If you invest money in the right items at the beggining, later it will be a pleasure to have them. By the term right items I mean natural decorations, to create for them an as much natural environment as posible. I use marine plants, wood, coralls, live rocks (most of them I buy online, from https://www.arcreef.com). And the natural environment is not only for them, it is for us too. It looks way better than the plastic ones. And I, personally, feel better when I know that my pets live a good life.