One thing I do is use a water pump with 1/2"tubing, which ends with a 1/2" shut off valve that I leave partly closed. This allows me to regulate the amount of water I'm running to the 1/4" drip tube that I'm branching off right before the valve. The water escaping the 1/2" valve simply serves to "stir" my res in the meantime

Did that make sense?


Oh, and I would say you need nitrogen just based on the severe yellowing.