Well actually I would just keep the water half a inch from the top , but I am no longer using the bubble cloner cuz I switched my stuff around and it wasn't giving me the consistent results I need so I am using Oasis cubes and Rock Wool cubes with Root Tech cloning gel but plan to get Rapid Rooters soon, I also use Jiffy Pellets they work well to so if I don't see a big difference with the RR then I will stick to the RT gel and Jiffy's. But the way I do things now is I used the containers that I used for my bubblers and flip one upside down for a humidity dome and it's working great and I have it on top of my flower cab under 2 T12's that are 6500K 20w each and I like it.... Works well cuz I take 8-10 clones a week using 2 containers and it takes 2 weeks to be rooted this way and having them staggered allows me to have my perpetual cycle going proper really soon!!!