beaslbob
2500 Club Member
One if this old engineer's pet peeves is the use of stablity to describe what are constant parameters. The two concepts are not the same with significant differences.
Constant means unchanging.
Stable refers to what a system does when it deviates from some "steady state" value.
Therefore it is possilbe to have constant, unstable operation and stable varying operation.
Consider for instance a yard stick you are holding vertically. It is possible to balance the stick in the palm of your hand. But with constantly moving your hand to keep it vertical. That is a constant (if your hand is fast enough) but unstable operation. Any wind that comes along and deviates the stick from vertical will result in the stick tipping over (unless you are very quick with your hand).
Now consider the stick vertical but held at the top. If the wind comes up the stick moves and gravity returns the stick to the vertical position. The stick may be bouncing around in the wind or even oscillating so is not constantly vertical. But because the system is stable no hand motion is necessary.
So in our aquariums some refer too a constant pH as stable. Not necessairly.
Is a constant 0 ammonia stable? Not necessarly.
And is a daily pH drop unstable? not necessairly.
So to me what is important is to increase the stability of your systems even if parameter do vary.
For instance, if you overfeed or a fish dies, do you get huge ammonia spikes that further stress the system? That is an unstable operation. But if the system (through plant action) immediately consumes the ammonia that is a stable operation.
And pH can drop each night. But if an increase of carbon dioxide results in more calcium carbonate being dissolved, the system will react to return the nightly ph drop to former values. A varying but stable operation.
So just a nit but to me and extremely important concept on how we maintain our closed systems. Stability is more important then actual values. And those values do not have to be constant. And don't assume that with constant values you have a stable system.
Just this old engineer's .02
Constant means unchanging.
Stable refers to what a system does when it deviates from some "steady state" value.
Therefore it is possilbe to have constant, unstable operation and stable varying operation.
Consider for instance a yard stick you are holding vertically. It is possible to balance the stick in the palm of your hand. But with constantly moving your hand to keep it vertical. That is a constant (if your hand is fast enough) but unstable operation. Any wind that comes along and deviates the stick from vertical will result in the stick tipping over (unless you are very quick with your hand).
Now consider the stick vertical but held at the top. If the wind comes up the stick moves and gravity returns the stick to the vertical position. The stick may be bouncing around in the wind or even oscillating so is not constantly vertical. But because the system is stable no hand motion is necessary.
So in our aquariums some refer too a constant pH as stable. Not necessairly.
Is a constant 0 ammonia stable? Not necessarly.
And is a daily pH drop unstable? not necessairly.
So to me what is important is to increase the stability of your systems even if parameter do vary.
For instance, if you overfeed or a fish dies, do you get huge ammonia spikes that further stress the system? That is an unstable operation. But if the system (through plant action) immediately consumes the ammonia that is a stable operation.
And pH can drop each night. But if an increase of carbon dioxide results in more calcium carbonate being dissolved, the system will react to return the nightly ph drop to former values. A varying but stable operation.
So just a nit but to me and extremely important concept on how we maintain our closed systems. Stability is more important then actual values. And those values do not have to be constant. And don't assume that with constant values you have a stable system.
Just this old engineer's .02
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