SO, I saw these a LONG LONG time ago from G.A.R.F and made a pair for myself about a year or so ago. these are SUPER easy to make and super cheap too. Materials: Currogated plastic sheet. (an old yard sign, election sign etc) Zip ties piece of reef rubble Drill and bit (i use a drill press) Cut the plastic into 3 or 4" squares. I usually make 6. the more even they are, the neater. I usually cut a long strip with a knife then cut that up with scissors into the squares. Drill a hole in 2 opposite corners and secure together with a zip tie. also tie a piece of rubble to them so they sink. the ones i have sink so you can gauge the size. from here, drop them in your sump or behind the rock. The pods will go inside and lay their eggs and use this as a safe heaven. you can get alot of pods in these things. they will come out and get eaten and or disperse within your rock work. I have two large ones in my sump and a good shake releases TONS of pods. they get sucked into the pump intakes and back into my tank. I just put a small one like this behind my rock.