I am not sure if your tank has cycled yet. How long has the tank been running? This is the time when most eager hobbiests make a big mistake...adding fish too fast. Remember, even after your tank cycles, livestock needs to be added very slowly (one fish per month) so the tank's biological filrataion has time to catch up with the new bioload.
Some people are like slinkies...they serve no real purpose yet can still bring a smile to your face when you push them down the stairs!:p
Have a great day! Brian