These XL biopellets don't need to be fluidized. Due to the curly shape of the pellet you can place these pellet in any kind of filter with high flow rate. Same material, different shape, same function. Many marine species require large and frequent amounts of nutrition, which in turn puts a lot of stress on your system and makes it very difficult to control nutrient levels. Examples of such species are Anthias fish, soft corals (such as Dendronephthya sp.), and filter feeders (such as sea squirts). This product has been developed for professional aquarists who want to supply their aquarium inhabitants with large quantities of food without negatively affecting water quality. The positive effects of NP-reducing BioPellets on water quality are based on the principle of immobilization. The pellets will allow aerobic growth of bacteria which will consequently consume nitrate and phosphate simultaneously. The bacteria will use up the carbon from the BioPellets, whilst nitrogen and phosphorus are taken from the water as nitrate and (ortho)phosphate. This conversion of organic BioPellets (together with inorganic nitrogen and phosphorus) into microbial biomass is called immobilization. The surplus of bacteria will be consumed by filter and suspension feeding organisms such as sponges and corals, or skimmed off by a protein skimmer. Both NP Reducing BioPellets contain 100% pure biologically degradable polymers and contain no fillers or anti-oxidantes which can be harmful for your animals. Color and shape may vary per batch. Some NP Reducing BioPellets XL can contain some small black spots, this is normal and doesn’t compromise the function of the pellets.