I have just completed the daunting task of drilling 2 holes in my 30G. Consists of two 3/4 inch bulkheads that lead to two 5/8 inch hoses. Connected everything to the sump and turned everything on. After adjusting everything to make sure the water level is just right I am hearing intermittent gurgling from the overflow. FYI - I do not have an overflow box installed. It just goes from strainer to elbow and slopes down to the sock in my sump. I understand it is the siphon going in and out. Should I use an overflow box or install a gate valve?