My rocks are good. One side is 15 month old, and one side is 6months old. The newer rocks were cooked, and the tank has never had high nutrients, or any sand bed, even when i had a ssb it was not around of under the rocks. I have some slime of a solid peice of limestone, non porous and certainly in high flow. Layton, it's not a rock issue.
TM, aready a lot of flow, anymore and the water would have trouble staying in the tank.
Have dropped back the CO2, and started dosing Kalk last week, so will see what happens. May try vodka??, or vinegar, not sure, will read up on it's effects.
thanks all.