It might also be that you are not adding enough. You can use this calculator to determine how much you need to add. http://www.kademani.com/reefchem.htm.
Jorge
Did you check that the washer that goes between the regulator and tank was in place? You can use soapy water when you get the tank refilled to check for leaks.
Jorge
Actually that is not correct. It is better to place the reducer as far away from the pump as posible, because the smaller pipe will add a big head loss by means of friction.
Jorge
Do a search for float valve in US Plastic. They have mini float valves with 1/4" fittings for this purpose. They are just like the kent float valves, but for half price or less.
Jorge