Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
Yes, they can get algae. Although they seem resistant to most varieties, hair/thread algae will grow in them.
Fortunately, they can be put in a bucket with water, and blacked out for extended periods without any harm. A week usually does the trick, and although nothing looks different, after being returned to the tank the hair/thread will disintegrate. I forgot about them once for a month, and they were still fine. I've heard in their natural environment, the water freezes over and blocks light for three months or so out of the year; so I guess that's why they have such extraordinary tolerance to blackouts.
The interesting question is what if a Marimo ball, which is a specific kind of cladophora algae, gets infested with any of the other dozen or so invasive varieties of clado? I think that's why some people believe Marimos can "turn" invasive and spread onto plants, there were actually two types of algae present. Not sure if the blackout trick works for that, would be interested to find out.