You need to do a lot of reading of the 'stickies' at the top of this forum. Please!
Are you doing any water testing? What are you testing for and what are the results?
Small tanks make it harder to keep things stable. And a 6 week old aquarium is just barely, if even, ready for corals. I wouldn't try a clam for at least 6 months, It takes a good tank at least 6 to 12 months to mature. Clams really need stable, mature environment. A 6 week old tank is way too young for any difficult to keep animal. And clams require a good light, what kind of fixture do you have? Some nanos come with good fixtures and some come with real junk.
Please don't rush things, you'll end up killing stuff, get frustrated with the hobby and quit. Take your time and enjoy what you have. In the meantime, read, ask questions and learn!
