only thing Algae does thats really bad is algae and the planet ends up competing for oxygen so aslong as the roots have air it should be fine so if it's in the res and closed with no oxygen then the roots have less air and there for can lead to starving the plant of oxygen thats why dwc is good cause not only does the plant get the nutes but constant air being pumped in as well so on top of rocwool not so bad