Originally Posted by Delapool
Have wondered on that siesta rule myself. Is that pretty certain?
Just curious. I could easily swap to just a very short lights on in morning to check tank and then the bulk of light on during the afternoon/night. That's very interesting.
Well it is a tough one really. I think the siesta idea came about for many reasons, most notably for allowing co2
to build up in a non injected tank, which it does. There are many arguments for and against this though with the ultimate answer from what I have read is that there really is no noticeable difference when using a siesta period. This is especially so and even more unnecessary in injected tanks. Plants will happily grow for the full photoperiod given the right conditions.
There are arguments that fluctuating co2
levels can be bad for plants due to the reasons mentioned in the last post about rubisco. Others arguments are that algae need much less co2
than plants and so after a few hours in a non co2
tank conditions become favourable to algae and less favourable to plants so by allowing co2
to replenish plants stand a better chance. Having said that, plants cannot compete with algae for anything so I believe that this is a moot point, it's that fact that plants are healthier with correct levels of co2
that keeps algae at bay. some people believe that algae wait for triggers produced by unhealthy plants to bloom. From my observations when plants are not happy algae tends to follow.
What i found in my Walstad tank was that they were not very healthy environments for fauna, meso-fauna, bacteria etc. The reason is that these tanks lack oxygen, especially when one doesn't have any flow, which sometimes I didn't because my Betta didn't like getting battered around the tank. Interesting calculations show that in still water oxygen takes years to diffuse in to lower depths. In a soil tank with lots of decomposition by bacteria, the oxygen demand is huge. As you may be aware Walstad advises against surface agitation (until recently) as not to allow valuable co2
to escape and so you do not get much oxygen coming in either. If oxygen levels are too low, organisms will not thrive and so net co2
production will also be low. Plants need oxygen too as you know they are not just producers. Allowing good surface agitation provides atmospheric equilibrium levels of oxygen and co2
which maximises bacterial activity and thus co2
production that may be captured upon escaping to atmosphere. Although co2
in equilibrium is indeed low, it is there and it is there all the time. What does this have to do with siesta periods? Well it suggests that these are not needed even in no co2
tanks. Diana herself now advocates good flow and surface agitation as she has observed that this is the reason people trying her method are reporting failure.
Focus on plant health rather than algae. Healthy plants seem to keep algae in check. Why? No one has the definitive answer but there are many viable reasons. We could go in to this more in another thread maybe.
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