I have a light algae problem that takes about two weeks of buildup before its visible enough on the front glass for it to bother me much. I keep snails to keep it in check overall, and mostly bought this scrubby magnet for if guests are coming over or I just feel like cleaning something.
I have found that I like to use this item in a scrubby motion rather than taking long strokes, it seems more effective. However, anyone using this should be careful nothing gets trapped between it and the glass on either side to avoid scratches. When moving the magnet across the glass the interior half "jogs" a bit which actually increases the scrubby motions, and I think helping to remove algae more quickly.
Had I realized just how large the medium is in relation to my tank I would probably have bought the small, because even though it would take longer the thing is very effective so it wouldn't take that much longer, and it would fit better into the nooks and crannies of my tank (making it easier to avoid plants, etc). That said I like the thing and it performs its one job successfully.
works great , the kids likes to use this , less work for me
Really great product and cuts the cleaning time down significantly. You do have to watch out if you have sand because it can get caught in the tool and possibly scratch the glass. Just go slow if you have an easily disturbed substrate and you should have no issues.