What is stable enough?

ReefGazer · Nov 1, 2018

I read a lot of threads discussing the need for stability of water parameters. What is your definition of stable?

For example, what amount of alkalinity fluctuation during the day or over a week is okay and still considered stable for a mixed reef with lps, sps and some softies?

James M · Nov 1, 2018

Yes it’s is considered for all types of tanks .

Joe Batt · Nov 1, 2018

I would say 0.5dkh or less daily would be stable for most SPS. That said even better to be 0.2 dkh or less a day.

Larry L · Nov 1, 2018

I think sometimes people take the idea of "stable" too far, and treat it like it means "constant". Some values naturally vary over the course of the day. FWIW, when @JimWelsh was developing his alkalinity monitor (i.e. the Neptune Trident) I remember him telling me that at first he tried to control his dosing so that his alkalinity stayed constant all day and night, and he thought his corals actually looked worse, and that they looked better when alk was allowed to vary naturally over the course of the day but maintain a constant baseline. I don't recall what he said the daily swing looked like, maybe he can chime in.

Randy Holmes-Farley · Nov 3, 2018

Alk stability is seemingly much more importnat than calcium or magnesium stability (although magnesium never should be unstable due to the very slow demand) because it is used much more each day on a percentage basis than calcium or magnesium, and coral calcification is usually dependent on it (not true for calcium or magnesium).

IMO, changes of 0.4 dKH or less seem adequate day to day, but there are lots of definitions of what stability means (hour to hour, day to day, week to week) and the answers are likely different.

Folks with very stable alk (+/- 0.1 dKH or less) using controllers and automatic dosing report improvements, but whether that is real or a placebo effect remains to be seen.