I have a 55 Gallon Fish Only tank. Operation a Tetratec PF300 Wet/Dry with one powerhead for counter circulation and about 60 lbs. live rock. I have one extra 10 gal. tank and various air pumps and other stuff. Is there a way to hook up the 10 gallon to the 55 to give more water volume, hence better eco? Some one mentioned a refugium. I dont know what a refugium is. If someone could be so kind as to shed some light it would be appreciated. Thanx in advance. 