CO2 Mist and Light Intensity


Junior Poster
Oct 1, 2007

I've been wondering about something. My 60 Gallon tank uses a mazzei to mist CO2. The pump driving it is underpowered, so most of the CO2 enters the tank as mist as opposed to dissolved (or at least I think it does judging by the amount of mist). The plants seem to like it just fine and it doesn't appear to bother the fish, but I think the mist may reduce the effective light intensity reaching the lower level plants.

I don't have a light meter and am not sure that they are submersible anyhow, but simple physics suggests that the light is diffracted by the countless bubbles, throwing more light out the sides of the tank and leaving less to reach the bottom. My only "experiment" to test this is to turn all the lights off in the room at night with only the tank lights on. With CO2 mist in the tank, the room seems brighter. Not a lot, mind you, but enough that I notice the difference.

For information purposes, it's a 58 gallon tank, 20" tall with about 3 to 4" of substrate. Lighting is via 196 watts of PC florescent with a mix of 10K and 6K lights. Rotala indica grows very slowly and thin (with small leaves) until it reaches the upper half of the water column, at which point it reddens up, the leaves grow larger and it really takes off. Ditto hornwort and other usually fast growing stem plants.

I know that even bubble-free water attenuates light, but the slow growth of low level plants I'm seeing with the mist seems very slow.

Has anybody ever tested the light attenuation due to mist? I'm sure bubble diameter and the density (number of per unit volume) of bubbles matters a lot, but perhaps one can show that the effect is small and I'm imagining all of this.

Tom Barr

Staff member
Jan 23, 2005
No, but it's not hard.

I can do it sometime. Bug me later.

Tom Barr