ZISS Bubble Bio - Moving Media Filter - ZB-300 review On first unpacking this filter I am immediately impressed with the quality, the box comes with 2 packets inside. The first contains the suction cups and Ziss air valve ZV-4, in the second comes the main filter itself. The unit is solidly constructed with everything obviously well thought out, coming in at 250mm high x 88mm footprint its certainly a neat and compact looking unit. A four point suction mounting system so when this unit is placed it will stay where its meant to, and has a separate Ziss ZV-4 airflow valve for fine tuning the water movement within the chamber. You can even tune the direction you want the water outflow to head in as the top cover will rotate. Perfect if you are looking to direct some water movement in tank or in a sump system Preloaded with Ziss ZM-1 media. This micro media is just 7mm high by 7mm diameter, yet has a huge surface area to hold onto any bacteria. Access to the media chamber is via a separate removable base cover that contains a coarse filter sponge to prevent any unwanted objects entering the media chamber. The air inlet is in a similar style to a sponge filter and is fed via a solid tube that is moulded inside the main chamber body. My plan is to trial this on my 400litre rack system as a part of the process however the only issue I can see with the product is a lack of sizing information as to how many litres this unit will handle. I am wondering if the ZB-300 refers to the litreage it can handle however for now lets wait and see how it performs over the coming months.