I read in a book that with a planted tank you must minimise surface agitation to reduce oxygen content in the water. Is this true? 1. Does this mean I must lower the outflow pipe of my filter to be 5cm below the water or must I rather use a spraybar? (Filter rated at 1100 l/hr) 2. What about my powerhead pumping bubbles through a venturi into the tank, do I still need this? (Powerhead is also rated at 1100 l/hr).