We are almost 4 weeks into our Biocube 29 and the green soft algae is growing on the glass. I've read this is part of the normal process then we read it may be too long a light period. We have changed the filter and also did a 20% water change as well as cleaning the glass. Are we supposed to let it grow on the glass until it turns dark green or black then clean it? We have had our water tested by the lfs several times and it is good. We don't know what to do at this point? Thanks everyone!