Planted Tank Guru
Join Date: Dec 2004
Location: Skagit County, Washington State
All of it like around ~ 1/4 cup in volume... I would consider getting some small pea sized crushed coral and a small media bag instead... The oyster will work, but the cc will work faster. I use to put three or four 3 inch plus oyster shell (halves) in my XP3 and still wound up with calcium deficiency, even though the KH was OK, or so my test showed.
I'm sold on crushed coral now, at .99 per pound at the LFS. Of course oysters taste great. But no more calcium deficiency at least, if I'm careful. My tap is like zero KH GH, however and 5.2 pH before I power head it, so take that in mind.
Three Tanks...Eheim 2128 & XP3-90G, Eheim 2128-65G, Eheim 2232-25G.... Tek 4x54 watt T5-90G, Aqualight 96watt PC 65G low tech, 65 watt Aqualight-25G.... Hydors-90G & 65G ... Flourite in 90, 65, & 25 Gallons, .... Auto Water Change/Auto dosing on 90 & 65 gallon..... AGA member......