Undergravel Filter - 20L or 29 Gallon - 30 in. x 12 in.
The Perfect-a- Flow Undergravel Filter is a biological filtration system for fresh or saltwater aquariums. The filter circulates water through the gravel bed and oxygenates it for beneficial bacteria growth. The slots on the filter plate have been designed to draw water evenly over the entire plate from front to back and left to right. The high tube connectors are molded into the filter plates to offer a secure grip onto the one-inch diameter lift tubes to keep the tubes from being knocked out by fish and preventing gravel from falling under the filter plate. There are four tube holders and caps. The Perfect-A-Flo air stoneprovides a  flow of fine bubbles. A 3/16 inch ridged tube connects to the air diffuser inside the uplift tube and will attach to airline tubing at the top of the uplift tube. When using an airpump and airstones use two uplift tubes per plate.  The fish protector is molded right into each elbow to prevent fish from entering the uplift tubes.  The Perfect-A-Flo Carbon Cartridge (not included) will fit into the fish protector.  These cartridges contain top-quality activated carbon to remove harmful gases, odors, and unsightly discoloration.For powerhead attachment place the one-inch uplift tube on the outside tube holder. The powerhead should have a flow rate of 100-140gph. Use one uplift tube per plate when using a powerhead. Using a powerhead provides a higher flow rate which cuts down on algae growth and requires less maintenance, however, powerheads are harder to conceal.