NFP Nitrate filters and Flow Rate | D-D The Aquarium Solution
Question: 

A question about fully automating the filter - the instructions state to have 2 water feeds - one slow on all the time and another controlled by solenoid / redox control.

 

Would it be ok to have the redox contolling a single inflow - ie -  with a pump being switched on or off depending on the redox?

 

Answer: 

Switching off the pump like this will not allow you to really get the most from the unit as you will not have a continuous supply of water and the redox will be continuously going up and down which is not beneficial.

By having a continuous flow the bacteria grow to meet that flow rate and the extra water from the bypass is really there to prevent the redox from getting too low so that you get the sulphur smell.

Use as described in the instructions will allow you to produce more zero nitrate water which is what you are trying to achieve.