RTR said:
RA - the pH changes from CO2 supplement (really from the carbonic acid of CO2 dissolving in water. a very small percentage of the total CO2) are completely trivial to the fish and the tank's metabolism. Carve in stone over your tank: There is no such thing as pH shock. Osmotic shock, from large and sudden changes in the osmolarity (most commonly read as TDS or as electrical conductivity or resistance) can be dangerous or fatal to fish. CO2 supplement has almost no effect on TDS, undetectable by ordinary hobby-level testing.
Thanks, RTR.
Tom, this is what I was referring to when I said:
"Most of the "gurus" on those sites do not run CO2 24/7. In summary, they don't feel it is necessary and that pH swings caused by CO2 injection are not the same as swings caused by other means and are not harmful to the fish. I haven't yet surmised where they get this information from. Does anyone know?"
I did not know how much of an effect, if any, CO2 had on TDS.
We use pH shift against known and tested KH to judge CO2 concentration, but with a huge caveat - KH tests can be distorted by the presence of organic acids, non-carbonate buffers, etc. so may not in all tanks have any realistic relationship to dissolved CO2. In most tanks and most water supplies, it is fine and quite useful, but certainly not in all.
Exactly. I have read *many* accounts over the past few days of people who jack their CO2 to levels of around 70-85ppm, with no stress to the fish whatsoever. Obviously they do not have "super fish", so there has to be something different about their water -- or their CO2 delivery -- that is different from others.
Carry-away lesson: Ignore dark-cycle pH shifts - the fish do, they never notice so far as we can tell. If you wish to solenoid and timer control CO2 supplement to match or slightly lead the light on/off times, feel free to do so. The shift in pH to baseline (non-CO2 supplemented levels) does no harm whatsoever - the osmotic shift, if any, is undetectable. If you elect to run CO2 24/7, all you need be concerned about is the dark cycle CO2 is not excessive to the point of sedating the fish and/or affecting their respiration rates.
I am far more comfortable shutting it off at night. The pH swing really doesn't bother me at all.
I think what I was trying to find out is this: if it takes *less* time to get CO2 to your target level in the morning, then your plants have more daylight hours of optimal CO2 levels. If this holds true, then
a) can CO2 levels be lowered overall?
b) is it better for the plants to have more hours of pearling?
Example: My target level is 25ppm. I shut my CO2 off at night and it takes me 6 hours during the day to get the CO2 to that target level. This level produces some really awesome pearling for 4-6 hours a day.
a) If I do NOT shut the CO2 off at night, then it only takes me 1-2 hours to get the CO2 to my target level and therefore the plants could very well have 10 hours of awesome pearling.
b) If I do not shut the CO2 off at night, and set my target level for 20ppm instead of 25ppm, then my plants could have 10 hours of
good pearling.
If a) and b) are true then is b) equal to shutting the CO2 off at night and getting 4 hours of awesome pearling?
Obviously, from the above, I'd rather run at lower CO2 levels on some of my tanks. My Boesemani males will start to thread if I push CO2 past 25ppm and they will all appear stressed at 30ppm. The duboulayi and parva bows in my other tank show no stress at all until the CO2 gets to 35-40ppm.
Neither of these tanks is over-stocked, btw. The Boesemani tank has 13 bows, 7 of which are juvies at a max of 2". The other six are adults at 3+ inches. There are also 7 Goo obo gudgeons that run from 1-1½" in size in that tank. Two amano shrimp that I've seen, I originally bought 5 and they could all be there for all I know
The other tank has 6 duboulayi juvies that run from 2" to 3½" (they can get to 5-6"), 6 parva juvies (largest is maybe 2", they max at 3"), and three 2½-3" clown loaches.
Roan
