A 6100 is a lot of flow for a 90, I generally would advise a 6000. If you feel you need less you can likely trade someone transformers as that is the only difference. Many people want to upgrade and the transformer you have sells for $74 and the smaller one is $36. The pulse should stop in night mode and the pumps stay at what ever you set the bottom knobs to on each channel. During the day the pumps pulse top to bottom, at night thay stay at the bottom knob.