The Bio Filter: The heart of every Koi pond In the past, bio filters were built much too small. But those days are over. Today, volume is the key. The bio filter is used in the pond to break down or convert the two fish-toxic substances ammonium and nitrite. And you can only count on excellent water values ​​if the so-called nitrification in the bio filter runs well. A few years ago, the size of the bio filter was not given much attention in koi ponds. Today, people are wiser. More than just a few ponds have shown that a pond that functions long-term and in which the koi are kept for growth only has correspondingly good water if the size of the bio filter makes up at least 5% of the system volume. In ponds in which an extremely large number of koi are kept or the koi are fed beyond measure, the bio filter should even make up up to 10% of the total volume. In indoor ponds and very small ponds, it is even recommended to increase this value even further. So if your new pond has 20,000 liters, the volume of your bio filter should be between 1,000-2,000 liters. Rapidly degrades toxins to keep fish happy and healthy Trickle plate on top and bottom to distribute water evenly throughout the filter Aeration System is installed and is ready for connection (outlet 3/8 inch hose nozzle) Lid included – MKC Filter Media included – Plug and Play. PE plastic is our preferred material for pond and filter construction. And there are reasons for that. There are many reasons why we only use PE in our pond and filter construction. But do you know what one of the most important is? If a PE weld is properly made and therefore leak-proof, then it will be leak-proof forever. At least we are not aware of any cases where ponds or filters have subsequently become leaky at some point. This is very well known for other materials. One reason for this is the high elasticity of PE – in other words, it cannot tear, but can easily compensate for certain settlements in the terrain or the expansion and contraction caused by the different water temperatures in summer and winter. This item must be shipped freight and will be charged a $250 shipping cost at check-out. Please note that after the carrier receives your order, they will contact you to schedule a delivery time. They typically will require a 4-hour window or more for delivery. An adult, 18 years or older, must be present and available to sign for the delivery.