Casuarina cones are similar to alder cones but are quite a bit larger and have a unique look to them. They are benficial for their tannins (recommended to lightly boil first, the longer you boil the more tannins you will lose. It I'd also a great place for the growth of biofilm. They have many nooks and crannies so that there is always food that only baby shrimp can get too.
Boil 5-10 minutes before use, the longer you boil the more tannins you will leech out. (they may tint water slightly but tannins are beneficial for all aquatic life)
Quantity: 10, 20