Wisely spoken, Hoppy.
Hoppy at this stage of the game for me I could clearly say based on my own personal experience that high flow is not necessary to grow healthy aquatic plants in an algae free environment long term. It really depends on alot of conditions, but the point I'm making is higher flow is not an absolute. I've kept filterless nano tanks long-term with no algae and very healthy plants. So other than stirring in some dry ferts with a spoon and having a shrimp crawl around the plants grow healthy for a year with no algae issues. So I would have to assume they arent' getting much in terms of flow. That's not to say that there could be a case where higher flow might help someone, but it still hard for me to comprehend that you need anything more than alittle movement to move ferts and dissolved co2 around two to four feet of water.Growing aquatic plants doesn't require a fixed, immutable set of conditions, or else the plants all die over night. I am a good example of someone who can grow plants under far from ideal conditions. You can grow plants with just fish poop as fertilizer, with no filtration, with low light, with algae all over the place, etc. What we are trying to do is grow them well, healthy and vigorous. That is what requires the good conditions, including good water circulation. As I see it, the real dispute is over what constitutes good water circulation. That issue is still up in the air. But, the trend seems to be towards a lot more circulation than we used to see in planted tanks.
We went through something similar with light intensity. We kept learning that we needed a lot more light than we were used to. So, people kept adding more light. Eventually we reached the point where we were using more light than we needed and causing as many problems as we were preventing. Perhaps water circulation will follow that path too.
Today I picked up a little more information. I was, along with a couple of other guys, helping Tom Barr move a 120 gallon tank into his house and we were talking about CO2 a little. He knows I have been puzzling over the need for so much water circulation. He mentioned that he had used his expensive CO2 meter to measure the ppm of CO2 in his 180 gallon tank, and asked me to guess what the results were. This tank has very good water circulation compared to anything I have had, with big Aquaclear filters and a big pump driving them, plus dual filter outlets and inlets in the tank. The results he got were: about 120 ppm near the filter outlet where the enriched water enters, about 40 ppm near the middle area of the tank, and 10 - 20 ppm down near the bottom in the middle of a bunch of plants. You have to admit that is astonishing. He has only cardinal tetras and some pencil fish in there - small fish. None were bothered by the CO2. (He is quite sure that larger fish would have been very much bothered by those levels.) And, even with the great circulation he had, the gradient in CO2 concentration was way beyond what he expected. So, he now has a big modified powerhead, with the model boat propeller modification, at one end, adding a whole lot more circulation.Hoppy at this stage of the game for me I could clearly say based on my own personal experience that high flow is not necessary to grow healthy aquatic plants in an algae free environment long term. It really depends on alot of conditions, but the point I'm making is higher flow is not an absolute. I've kept filterless nano tanks long-term with no algae and very healthy plants. So other than stirring in some dry ferts with a spoon and having a shrimp crawl around the plants grow healthy for a year with no algae issues. So I would have to assume they arent' getting much in terms of flow. That's not to say that there could be a case where higher flow might help someone, but it still hard for me to comprehend that you need anything more than alittle movement to move ferts and dissolved co2 around two to four feet of water.
I agree. As usual, all of his tanks looked very good. He had a several day power outage while away, so he lost some plants and fish from that, and is still cleaning up the tanks, but they looked great to me, all over. Some day it will be possible for someone to say with confidence that we need at least X ppm of CO2 for the plants to do their best, but I don't think we are near that yet.Well I did say 2 to 4 feet. LOL.
My question is how are the plants doing on the far end of the tank where the co2 ppm was lower? Is there any difference between the ones near the return? I could tell you I have a 4ft tank with an eheim ecco and it effectively turns over the water once per hour. There is a spray on the left piece of glass angled down 45 degrees with a ceramic diffusor right below it. So the co2 goes up, hits the spray bar and is pushed left to right across the tank. There are two main rotala rountifolia groupings. One right near the spray bar and one on the far side side and their is no difference in appearance between the two groups either in fullness, color and pearling activiity. The testing might open a whole bunch of interesting information. I certainly will not doubt any of the readings from the tests taken, but one needs to just look at the plants to see what is necessary. And whether the co2 ppm is 100 near the return and 10 near the opposite side if the plants are growing great it tells me I don't need additional circulation and/or maybe we don't need 30ppm co2 as well. I don't believe any parameter works in a vacuum including circulation.
Vary nice of you to offer your tank. I am in the same position as you, my "Financial Manager" wouldn't let me do that either.Yes, I suppose I'd be pretty miffed at myself if wound up with tons of algae all over the place after shutting down my main fliter just for kicks.
Well, that rules me out of conducting the test. My "Financial Manager" (the Mrs.) would never let me get away with buying another tank (or two)...well, not anytime soon.
I continue to find this discussion very interesting. I have been reading Tom Barr's thread as well. It seems hard to imagine with that much flow that he has such a variance in CO2 measurements, but you can't argue with the facts. The next question is why? Can some plants actually take up the CO2 so fast that he'd get such fluctuations? Then I ask, so how do we overcome the fluctuations if at 18X turnover he still has such fluctuations? Do we plumb our tanks so that the CO2 enriched water is released every 25-30 cms around our tanks? It will be interesting to see if there is any resolution....http://www.barrreport.com/co2-aquat...eal-time-data-localized-co2-ppm-readings.html is Tom's own report on his CO2 measurements, for those interested.
I admit that I have no ideas at all about how to measure the effect of water circulation. It is easy to try increasing the circulation and see what happens, but if the plants grow better, you lose some of that increased circulation, canceling out the effect. You can also reduce water circulation and see what happens, but who wants to risk an algae outbreak? The idea of 2 otherwise identical tanks, one with a powerhead, preferably a Koralia, adding a lot more circulation, seems to be the best experiment that is possible for one of us to do.