Nitrate Spike after i added a Protein Skimmer

[TransferOfRisk]

everything seemed great in my reef tank and tuesday i added a protein skimmer.. reed octopus... nitrate then was less then 5ppm and no signs of amonia or nitrite... ph was @ 8.4

today i go and check my tank after cleaning out the skimmer for the 3rd time (very little amounts maybe a quater of a cup a day) and my Nitrate spiked to between 40ppm and 80ppm..

the tank has been set up for about 8 months .. it has a 2 inch crushed coral sand bed.. about 250-300lbs of live rock... corals(mainly soft)... and about 3 fish.. power tang.. sail fin and a damsile...

not sure what is causing this.. however i do have a wet dry.. and was told to remove the filter pads from the 2 boxes.. im thinking about replacing those as of right now to see if that helps..

what could be causing this

 

[TransferOfRisk]

update

i have started doing a water change25 gallons.. im also making more RO water.. i also have cleaned the filter pads... and added a carbon pouch.. waiting a few hours before i do a water test.. before i started the water change i was starting to see a greenish tint in the water... all fish are accounted for and none of the corals seem to be affected so far..