i would worry about where the amonia came from right now, amonia shouldnt be detectable at anytime if it is detectable even in small amounts its harmful but is also a huge sign that your tank isnt stable.
if you tank is on the stable/unstable fine line then a ittle time has to be given for the balance to work out.adding anyhing n ow or in the near future could keep it on this fine line.
another thing to note is inverts are very sensitive to salinity spikes and temp so be sure to make sure they are always consistent.acclimation is very important.
if your shrimp just molted it is also at its most vulnerable period, what do you have for fish?? notice any bad crabs you didnt buy??
__________________
........
|