just curious.... air stones
 

i was just thinking, ive been told many times about not using any air stones or air devices in planted tanks, especially with co2. now the co2 part i understand...

but wouldnt a non-co2 injected aquarium be ultimately unaffected by air devices? i understand that the plants consume co2 and expel o2, and fish the opposite... but if i had an air device creating a large increase in surface area for gas exchange, wouldnt i exchange just as much o2 as co2? it would be a wash, no?

No because the air you are putting in contains more o2 than co2. The plants consume the co2, give off o2. It's dissolved in the water and will naturally eventually gas off. Air or heavy surface disruption speeds up this process to where the co2 is removed rapidly and all that is left is o2. This is where a "mid day siesta" comes in handy. By shutting the lights off mid day for a few hours the co2 levels rise a bit creating more co2 for the plants to consume when lights come back on. If lights are left on for the solid 8,10,12 hrs they constantly photosyth drawing the co2 way down. Siesta recoups co2 for them

:shock: couldn't have said it better! Spc if there's no co2 injection going on what your fish give off your plants NEED that because there is no add co2 so what they got gotta stay there for them. But also you wanna look at how much the "air devise" you wanna use gives off; like a normal sponge filter set up with a lil air pump will work vs a whole bubble wand put in the 5g planted won't cut it.

but even though the co2 levels would most likely remain lower with surface agitation it would still provide a steady supply of co2 from the surface, more so i would think than without one. has anyone ever really accurately tested just how much co2 fish produce? im not bucking the system, just curious :)

The problem in ONLY measuring the fish co2 output will be the factor of what comes in with your tap water :-) so to ONLY measure what the fish give out will be next to impossible.
If it wasn't for the move and half my fish stuff being gone now I could post you a chart where I had tested co2 levels over 1 week each day; then added air on low set up and its results over few days and then upping the air (using a valve). Needless to say at the end of this I had dangerously LOW co2 and stopped the test. :-) But I don't have the exact figures (my fish book) any more sorry :-(

I think there may be a misunderstand here. Surface disturbance allows CO2 to dissipate from the water, it does not bring it in to the water, ever. Oxygen enters the water, CO2 leaves; this occurs at the surface always, but adding air bubblers and surface disturbance quickens it.

The reason this is detrimental is because it takes plants some time to assimilate the CO2 and it gets removed before they can. I go into this aspect in detail in Part 3 of the series stickied, esp para 3, 4 and 5 under "Filtration," here's the direct link:
http://www.tropicalfishkeeping.com/a...um-part-34858/

Byron.