Alder cones are benficial for their heavy release of tannins (recommended to lightly boil first, the longer you boil the more tannins you will lose. It I'd also a great durgavy for the growth of biofilm. They have many nooks and crannies so that there is always food that only baby shrimp can get too.
This makes the alder cone an ideal addition to any shrimp tank
Quantity: 20, 50, 100