To ξέθαψα, αλλά αξίζει
Tom Barr
http://fins.actwin.com/aquatic-plant.../msg00151.html
Many suggets that the pearling we often see after a water change is due to air/O2 and other gases such as N sticking to plants and is not true O2 pearling. There are a few ways to address this to see if it is in fact "increased growth" or just sticky bubbles (This arguement has merit and must be addressed and ruled out/accepted). One way to test and see is: I recently tried something interesting with hair grass. I took replacement water that was at equilbirum with air and tank temp. So no air/gas, etc is going to come out of solution and stick to anything. Sound reasonable? There's no high CO2 etc from the tap water here, the buckets full of water have been sitting for a week and the tank and room temps are equal. Note, the replacement water is RO, no other nutrients are present such as PO4 which can increase pearling in less than 40 minutes if the tank is limited. I drained the water down to exposure the hair grass to the air. I slowly refilled the tank with the low CO2 warm water. Observation #1: The plants had no bubbles upon filling the tank. Observation #2: After 15-30 minutes, the plants began intense pearling, very intense. As intense as you could possibly imagine and I've ever seen. Anyone could tell and see this massive difference. Nutrient limitation is ruled out due to EI and ADA aqua soil(4 months old). Light is at 300 micro mol, plenty high for good photosynthesis. Plant health is good. No fish, no snails to speak of. Why would the plants not have bubbles after the water change, then formation occurs 15-30 minutes later? The water is at equilibrium so no degassing is going to occur. The only reason I can figure out to such a degree that influences plant growth like this is due to exposure to air for 5 minutes. What is in air that's not at high levels in the tank that would induce intense growth? CO2 in the gas phase. This shows/strongly suggest that aquatic plants can dramatically increase production and growth if they are supplied with a gas phase of CO2. It's a simple test and the observation #1 shows that it's not due to degassing tap water etc, it's due to the gas phase exposure to air. Mimicing this with CO2 mist is a generalized concept for that theory. So what about air just leaking out vs O2, the standard for pearling and aquatic plant growth????? Experiment no#2: I have a DO meter that measures O2 levels in water. O2 levels are strongly correlated with plant growth and production in aquatic ecosystems. O2 levels are used to determine productivity(true pearling) in a quantative manner in research science. This allows me to measure the rate of pearling or the rate of total plant and/or algae growth due to a treatment. So if I have a tank that's limited due to PO4, then add PO4, I see dramatic pearling increase and can verify this with my DO meters as well, often times by about 30-50% growth increases if the PO4 limitation is fairly strong. So this is a fairly useful tool used to measure plant growth in our tanks! Few plant aquarist have these devices, I think only George Booth was about the only aquatic plant person besides myself on the web that uses them for aquatic plants. So I tested the before and after O2 levels at the same time I did the water change above. I had 7 ppm(100% a tad over) before and 11ppm after(t= 2 hours) or about 160%. 60% higher O2 is something anyone should be able to "see". People huff and moan about various things to improve their plant growth, yet CO2 can increase the growth by 10X easily or 1000% faster vs ambient in submersed plants when the CO2 is in the dissolved aqueous. It is far more critical in terms of growth improvements in most cases than NO3 or PO4 etc. CO2 is also far more ephemeral than PO4 or NO3. Yet few test to see if the water change is really adding a gas phase of CO2 that increrases the plant growth, instead arguing it's just degassing water and never really getting to the bottom of anything. Talk talk, not test test. As far as I know, this is the first demostration without a O2 meter to show and confirm that pearling in this case was due to gas phase exposure to CO2. The backup with the O2 meter offers more support for the contention as well. If folks see intense pearling after a water change, and then for the remainder of the day(do a large water change early in the day), it generally means it's due to the tank not getting as much CO2 to the plants as it could. CO2 mist side steps adding a lot of CO2 gas into solution, rather, it leaves it in the gas phase. I've confirmed CO2 mist increasing the O2 levels by 50% without no change in bubble rate(contrst that to the 60% in the air exposure experiment!, I have 10% more to go, well, actually a lot more replicates
). I just simply switched from a mist injection from a reactor with 100% dissolving efficacy(All the CO2 is dissolved). I'm not happy with the CO2 measurment, so comparing the ppms is harder to do since the error overlaps between both treatments, but the bubble rate of CO2 delivered to both treatments remained the same. Also, the error overlaps, so that CO2 membrane KH reference idea is going to come in handy for very close precise measures of CO2. There was a reason why I looked into that. Once I get good CO2 measurements that I can be very confident about, then I can move forward and argue very strongly for CO2 mist. Many have already seen the dramatic effects of the mist method. Many complain there's too much growth and that such pearling is a distraction. But others like it and I personally do as it kills off algae as well and I like to push the limits of systems till they break or crash. I'm weird that way I suppose Regards, Tom Barr