Algae beneficial?

Not sure. Algae growth can support a host of micro-organisms, both good and bad. I rinse out my cutting container and remove any decaying debris weekly. Most roots prefer a dark environment.

So can soil. Usually, they balance each other out with no special attention paid by the grower. Plants thrive. Noses are reliable indicators of when imbalance does occur.

I haven't found light to be all that detrimental so long as it's not intense. Less work just to stick the cuttings into mason jars and wait, maybe changing the water every couple of days. It might be setting me back five days over a 25 day period, but so far, everything's rooting, though at its own pace.