Air on at night ?

[ian_m]

Saw something somewhere, where the CO2 was turned of an hour or so before lights off, but air via air stone turned on an hour after lights off (and off an hour before lights on) so as to re-oxygenate the water during the night for both fish and plants.

Anyone got any comments on this regime ?

One possible theory was that they had not got enough surface movement and fish were suffering lack of oxygen.

 

[Themuleous]

You can but it's not necessary in my experience. Some poeple like to de-gas the co2 to give the fish a break from it, but healthy plants will be producing lots of O2 so the wont be a shortfall.

Sam

 

[dw1305]

Hi all,

Saw something somewhere, where the CO2 was turned of an hour or so before lights off, but air via air stone turned on an hour after lights off (and off an hour before lights on) so as to re-oxygenate the water during the night for both fish and plants.

I would always have extra aeration at night, but whether you need it really depends upon how much bio-load you have, which fish you keep, how much water movement you have and tank dimensions. If you have very heavy planting this will reduce flow and the large plant mass will consume dissolved O2 whilst the plants aren't photosynthesising (when PAR levels are below the light compensation point (LCP)).

Even if things are fine normally, you may eventually have the "perfect storm" scenario with a combination of a slight loss of flow (filter needs a clean), larger plant load (tank needs a trim), fish with a high oxygen requirement (or an increasing bioload through growing fry etc), a relatively deep tank with a large volume to surface area ratio (a cube perhaps), warm water (water can hold less O2) and low atmospheric pressure (water can hold less O2) and you may run into oxygenation issues.

Lack of oxygen (or too high a CO2/O2 ratio) is a different problem from nearly every other one we may encounter in that if you get it right 99.9% of the time, but it goes wrong for the remaining 0.01%, you have killed all your fish.

cheers Darrel