| Most amps effect loops are for line level, e.g. for rack mounted gear, and not instrument level like you would use with your pedals.
Your best bet is to put pedals in front of the input (Bass-->pedals--->amp). If you have a rackmount compressor or eq unit then you would take the fx send and go into the rack gear's input, then the rack gear's output goes to your fx return. | 
