Agree with everything Sam said. One another point about the total cost to do this.... Remember you are saving yourself an hour or two every week because of not having to do manual water changes!
I use the
Arduino set up with two Spectrapure pumps that Sam mentions and it works great. You just need to upload the new code if you want to change the amount of water. You could probably even do this over wifi with the Arduino if you know how to code it. I am not sure if you have seen this done yet
@Sam Parker ?