when should i test my water??

[kingshrimp]

hi iam new to this hobbie and iwas woundering when is? or what time of day should i test my water? or does it matter? also once you get your water tests normal will they just stay the there? also will a protein skimmer drop your water test to safe zone?

 

[kingshrimp]

once you get your ammonia test to read zero will it stay that way?? can you do this if you already have if in threre