Hi Bala Sharker and welcome to TFF!
I can tell from the fact that every one of your sentences is packed with the names of fish that you are very excited to instantly have a fish tank! Its a natural desire! The really amazing thing is that you've stumbled on to probably the best place you could go to get lots of advice from a bunch of serious hobbyists, many of whom have walked right down the path you are on, but many years ago!
Unfortunately I have to agree with the others above that to get you started in the right manner, we need to help you realize that the core technology of a modern fish tank, the biofilter, is not "up and ready to go" until it has "qualified" as being "cycled." The terminology itself can be really confusing at first, not to mention the processes involved! The local fish shops (LFSs) are weak-willed and don't really have the guts to tell you that it might take 2 months to get your biofilter up and going.. they fear you would take your business and go elsewhere if they said that (not to mention that plenty of new-hires in the LFS don't have a clue about his anyway!)
So what is the alternative the LFS promotes? Its to just have your cake and eat it too.. just put the fish in before the biofilter is ready and let the fish provide the ammonia to grow the bacteria and get the biofilter started. Never mind that ammonia, even in tiny amounts causes permanent gill damage. Never mind that after some of the first bacterial species grows it will be producing nitrite(NO2) and that even in tiny amounts that causes permanent nerve damage. Heck! Those fish can't talk and "they look just fine, don't they?"
The other unpleasant thing to face is that the LFS will stock, even in most of the tanks, fish that are just totally inappropriate for beginners who have normal sized tanks, tanks like your 15G/60L. In fact, sometimes only a very few of their tanks have fish that are really good for beginner community tanks, sometimes about 6 tanks out of 60 on a typical pet store "fish wall."
So what should you do? Get mad? Ignore all this? Well, the truth is, if you can swallow it and stick with it, you're going to find a bunch of great members here and a wonderful entrance to a truly fascinating and relaxing hobby. The whole point of a fish tank is to relax, to get away from all the hustle and bustle and have your own place that you can look in to and enjoy. It doesn't have to advertise itself, it just has to be there for you. And one of the surprises is that the -process-, the process of learning and making the tank be ready and of maintaining it, can be much, much more enjoyable than you'd think! Anyway, I hope you'll become curious about fishless cycling and about taking the time while that's happening to learn all about the art of stocking your given size of tank with just the right fish for it and you.
~~waterdrop~~
