The Fluix Seed is an item added by Applied Energistics 2. When thrown into Water, it slowly grows into a Pure Fluix Crystal; its rate of growth can be accelerated by placing active Crystal Growth Accelerators around the Water block it is placed in. Because of the amount of time it takes for Seeds to grow they will not naturally despawn. If AE2 Stuff is installed it can be placed in a Crystal Growth Chamber to grow at a faster rate.
Its appearance changes depending on how much it has grown.