Knowdafish;4747588; said:To answer your question, "is it cheaper?". No, it will be exactly the same if it is set up to change the same amount of water you are changing now.
As far as how many GHP should it be set up to drip. That is totally up to you. How often do you do water changes now and how much do you change? With that info then the GPH question can be answered.