Just thought you'd like to know that you were absolutely right. The Chaeto is growing very well now. Almost doubled in only a week time! Even though I'm only turning on the lights when I'm at home and not asleep because of the cracked tube. It's cracked, but still doesn't let water in. (I know I know, not smart. I just want to keep the chaeto alive until I get my new - actively cooled - solution arrives.