Eheim 2213, 2 angels, 10 cherry barbs, 2 yo yo loaches, 4 bn. Planted tank w substrate for plants gravel overtop, 3 small driftwoods and couple small caves. No CO2, small amount of air.
If it was a kH problem why haven't i had it before.... Auckland water quality is pretty much the same isn't it? Also the same in other 3 tanks...
Yoyo's are a pretty reliable sign of stress as their colours go really pale... afta pH adjusted colour comes back pretty quickly and fish look much happier haven't noticed any problems with fish afta adjusting pH shift...they settle right on down and stop stress behaviour.
Only difference that I can think of have feed Nova tabs instead of shrimp pellets....