Every book I read has a different idea about whether CO2 should be left going day and night or only during the day. (I am solaniodless) Reason for: being that one reduces the swings in pH as the formation of carbonic acid drops off (During the night) From some of my studies of water quality at canterbury university I've seen that these pH swings occur in the environment and aquatic life has adapted to survive this. What should I do?

Hi Peet,

I can't tell you what you should do but I'll tell you what I do with a 250L setup.

Keep kH (bicarbonate) at or above 4 (a teaspoon of bakingsoda at every water change will do it (in Upper Hutt anyway)

I bubble CO2 at a rate of about 15bubbles/minute in a reaonably planted tank, not to lush at the moment (maintenance problem and old lights)

Anyway, my opinion, don't worry too much about pH swings and stabilise it a little with a mild buffer