This is a small magnetic tank cleaner for an aquarium. I chose a small one because I would keep this in the tank and didn't want a big magnet hiding the view of the tank.
I bought it from Amazon for a good price and bought other items to get free shipping.
The cleaner side (part in the tank) does a fair job or getting rid of the brown algae build-up. You do have to go over the same spot 3-4 times in order to remove it completely. The magnetic bond is strong and works well even with a curved tank.
It's been in the tank for 4 months straight and still performs well for a 37 gallon tank. If you have a larger tank, I would recommend the larger size.