one of the best suggestions I can give since snyperhank gave you the best answer.
Never trust a pet store clerk as they will tell you things just to get you to buy stuff ,
be sure to keep up on daily water changes till you get through the cycle. If you have a qt tank I would move the fire shrimp till the cycles done as he is the most fragile invert.
be sure to clean that canister weekly as they are nitrate factory's.
things like this prove qt tanks are beneficial , they also serve to observe new fish to be sure they eat and are healthy , and if you have a sick fish ,
how much LR
do you have it's best to have 1 1/2 lbs per gallon but in a tank your size for a good startup is around 40 lbs than build from there just be sure it's cured first,