Gfish said:
Hi,
I'm aware that having too much surface agitation in a Co2 injected tank is bad and understand the reason, but on a low tech tank is there an advantage to having an airstone, Venturi or excessive surface agitation? I.e over oxygenating.
The reason I ask this is, of the 3 tanks in my house, my daughters 2ft is the healthiest by far. No signs of algae. A bubble curtain along the back wall. Masses of plants some very slow but others fast enough to need a trim every few weeks. And it's never been treated to more than the occasional pour in fertiliser and a weekly 40% water change or so.
Gavin,
It's not really a good practice to link any one factor, like the airstone bubbles, to the tank's performance, or to compare the performance of multiple tanks - unless there is a specifically controlled comparison.
People are always doing this, even those who know better. You have to analyze tank performance holistically. What I mean by that is that there are so many variables. Not only are there many variables, but there are many degrees to the magnitude of those variables. All the effects of these variable add up to produce the performance we observe.
There is no way, given the lack of data about the tanks, that anyone can say with any certainty, what variables are responsible for what aspect of the performance. It's easy to draw illogical conclusions without any data whatsoever. Brainstorming possibilities for your reported observations cannot compensate for lack of precision or for lack of data.
Lets examine your statement for a second;
You have 3 tanks and one tank outperforms the other two. We have to assume that all three are planted tanks and that at least one of them is a non-CO2, non-Excel tank - but what are the other two? We know that flow/distribution makes a difference and that the larger the tank the more critical flow is. Are there differences in the sizes and is flow optimized in all three cases? Are the PAR vales similar across the tanks? Are the same plant species present across all three tank? Are the stocking levels high and are they more or less equivalent?
Is performance being defined in terms of the growth rates or in terms of algal biomass, or in terms of appearance or some combination of these metrics?
Unless we have solid data regarding these factors I just don't think it's a good comparison. Unless we have control of the metrics or control of the the application of nutrient/CO2 then all we really have is visual evidence of one tanks adaptability to it's particular set of environmental challenges versus the ability of another tank to adapt to
it's unique set of environmental challenges. Without the ability to measure and control the environments then the comparisons are strictly random.
The same can be said of the claim that the dangers of high energy lighting might be an overstatement. What are the PAR values? What are the conditions of the tank? What are the actual water/sediment nutrient content? How long have the plants had to adapt? What are the species in the tank? Are there floating plants that limit PAR penetration?
Steady state environmental conditions enable aquatic plants to make specific adaptations,
so it could easily be that one tank has stable conditions while the other two are unstable. Even if were such that the bubbles in this tank outgas CO2, the CO2 concentration could be stable enough during the photoperiod. Given time, the plants can adapt to very low CO2 levels as long as PAR values are not too high. About 50% of species have the ability to use bicarbonate. This function is immediately available under low CO2 availability. There is no waiting. Hydrogen ions are pumped into the water column which then shifts the equilibrium equation to the left and produces CO2 which is taken up straight away. Assuming a non-zero bicarbonate level, and assuming that a percentage of the plants have this ability then the high Rubisco efficiency plus the possible HCO3 conversion could be sufficient to keep the growth rates at a good clip. Nutrient content of the tap plus organic waste plus CO2 expelled by fish can be sufficient in a stable low PAR environment.
There are plenty of examples of thriving low tech tanks so this shouldn't be surprising. If the other tanks are not doing as well as expected, then it speaks to the techniques being implemented in those tanks, which should be addressed on their own terms, not by comparing their relative performances.
Cheers,