Some customers feed with a full reservoir of feed, let it run to a 1/3 full then top up with pH balanced water and feed this for 24-48 hours then re-fill with water and add the fertiliser and then repeat the process. Other growers just feed all the time. Always remember to use your flush taps at the end of you lines to remove any sediment in the pipe work, this should also be carried out once a week minimum, if the water is poor then more often as required