wow that was fast (RTN?)

[mark]

Well just tested the usual and nothing seems out of line. Not manually dosing anything as use a reactor and it's behaving (not spiking alk). Alk 10.2 dKH, Ca 410ppm, NO3 usually zero but now 0.2 but then did just loose a large colony.

Zeo or other, not sure if worth trying as thought people used more to get the colours than prevent RTN.