Fluval aquarium substrate "Stratum" ground for shrimp pool, is small Erdkügelchen. but which do not disintegrate in water. My plants grow super. Strangely, the beads of 2kg pack are much finer than that of 4kg pack.
I had since I use this reason no longer a problem with the tilting of the pelvis. Also Mulm (in Nanos always a vexed issue) there since her much less. I can only recommend this substrate!