Indicator Light Reminder: It works by detecting that water starts to overflow around the filter chamber due to the cartridge being clogged and the LED indicator light will turn on to remind you to replace filter pads HOB Filter, Saving Space: You can effortlessly mount the power filter to the outside of aquarium wall by the hanging design without taking up valuable tank space, and don't have to worry about disturbing fish when removing the filter for cleaning Water Circulation: The filtered water flows back into the tank in the form of a mini waterfall with the sound of a trickle, which helps an outflow that maximizes water agitation and oxygenation Adjustable to Meet Your Needs: The water flow speed can be adjusted through the top knob, max flow rate is 210 GPH. The intake tube can extend flexibly, adjust the length according to the depth of the tank. The water inlet is also with sponge to prevent small fish or shrimp from getting suck in Easily Replaceable As Need: hygger aquarium filter is come with 2 types of filter media; One is the filter cartridge consisting of dual-sided sponge cotton and ultra-activated carbon which more effectively filter out fish feces, food residues, remove odors and discoloration. Another is the bio-filter plate that provide larger surface area for support of bio filtration. Filter media can be added or replaced as needed, making it suitable for both beginners and experienced hobbyists hygger Aquarium HOB Filter Fish Tank Power Filter with Overflow Alarm External Hang-On Back Filter