nigel bentley
Member
Hi Clive, you are so right it's even created a hole in the substrate at the front.😂 Time to rethink, I will investigate into maybe 2 off the Koralia smaller pumps.
Thanks again
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Co2 troubles
- Thread starter lidz87
- Start date
Thanks again
nigel bentley
Member
I was thinking of going for two Koralia Nano1600. With the two external Aqua one filters, this will give me a x11 turnover even allowing for filter media and pipes etc. I think disregard huge powerhead will have a three fold bonus
1) Better water distribution
2) Less disruption for fish and plants
3)Will look nicer
Thanks for your help Clive
1) Better water distribution
2) Less disruption for fish and plants
3)Will look nicer
Thanks for your help Clive
Easternlethal
Member
Okay so this is thread is demonstrating what happens when we try to solve co2 distribution through flow without understanding diffusion.
Some people may know that takashi amano was fascinated by marine photography and consulted with oceanographers when refining co2 products for his ada brand. This is because oceanographers study fluid gas exchanges between the ocean and atmosphere. There is every good summary of the models studied here:
www.intechopen.com
There are various factors that contribute to gas exchange across a water surface: a) the boundary between the water and air (thickness, depth, and viscosity)( b) effect of current in creating turbulence at this layer (called 'eddies') and (c) effect of deeper layers underneath.
The same applies inside a tank and can be illustrated by this diagram:
So applying all this theory to your single pump configuration, the strong flow will cause turbulence at the top layer and a strong current underneath which will probably resulting in more co2 escaping than being distributed.
This is why I'm not generally a fan of powerheads in distribution flow.
Some people may know that takashi amano was fascinated by marine photography and consulted with oceanographers when refining co2 products for his ada brand. This is because oceanographers study fluid gas exchanges between the ocean and atmosphere. There is every good summary of the models studied here:
Near Surface Turbulence and Gas Exchange Across the Air-Sea Interface
Open access peer-reviewed chapter
www.intechopen.com
There are various factors that contribute to gas exchange across a water surface: a) the boundary between the water and air (thickness, depth, and viscosity)( b) effect of current in creating turbulence at this layer (called 'eddies') and (c) effect of deeper layers underneath.
The same applies inside a tank and can be illustrated by this diagram:
So applying all this theory to your single pump configuration, the strong flow will cause turbulence at the top layer and a strong current underneath which will probably resulting in more co2 escaping than being distributed.
This is why I'm not generally a fan of powerheads in distribution flow.
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Yes, I also prefer to have a more muscular filter, but I think Nigel is getting the picture now. It takes a while to learn this stuff. Hobbyists are not experts in oceanography or in computational fluid dynamics, so even when we offer sound advice, it's from10,000 miles away, we don't always see the whole picture and information can easily be misinterpreted. This is simply the nature of learning.
As you mentioned there is an optimal range of flow rate across the leaf surface, below which the boundary layer thickness is too high and which attenuates gas transfer. Above which simply batters the leaf and reduces contact time between the gas and the leaf.
Laminar flow across the leaf reduces the boundary layer thickness and allows penetration of the gas to the leaf membrane. We get all that. ADA hideously overpriced gear does not necessarily perform any better than simple DIY. One just needs to understand the basics of flow/distribution in order to conjure up a viable scheme.
In many cases, however, we've seen where the filter flow to the spray bars is insufficient and must therefore be augmented with the powerheads. This is a lot less expensive than buying a new filter, so there is an economic imperative as well.
Cheers,
Easternlethal
Member
Yes I know I'm belabouring things a bit and probably going over stuff that most people understand instinctively or have discussed already.
But I would like to do is propose a process that's just a bit more methodical as it can be helpful when our instincts don't produce the desired results. It's something I go through many times myself when fine tuning a tank, especially if I'm stuck with a certain aesthetic and don't have the flexibility to add more equipment or change flow direction. It can also help when extra fine tuning is needed later when plant mass changes.
So after thinking about how co2 interacts with the boundary layer in the tank, we can look at what kind of pump action we want. Do we want the pump to a) increase dwell time, b) deliver co2 somewhere specific or c) create turbulence? In this particular case we would want a) because the spraybar at the back is delivering even co2 across the width of the tank already along the surface to the front. Setting these objectives is really important because they can be different for each tank.
So the analysis would run something along the lines of: For a) we want something that can force fine bubbles deep below the tank and b) could be difficult because a pump itself is not providing any co2 because it is just moving water and we probably don't want c) it it drives out co2.
So for pumps we have to be much more sensitive to how it interacts with current from the spraybar and hard to get right even for experts, especially if it has limited flow power adjustments and narrow dispersion for the tank's configuration.
And the consideration of various solutions might involve: a) recognising that multiple smaller pumps might produce more evenly distributed power but the dispersion needs to be wide enough: b) considering whether wavemakers make things even more complicated and hard to control due to the eddies they create; c) evaluating whether the available pumps have sufficient control options d) looking at the type of nozzle - e.g should we use a normal nozzle, flat tip or wavemaker; e) exploring all available options - might a diffuser be better (especially if it's just one spot that Co2 is needed f) what about strengthening the filter pump or if not possible, g) supplementing it with additional atomisers, this quite common for weak filters?
Pump nozzle / output options
Non co2 injected pump configuration options:
These are just examples of things to consider before just reaching for the nearest available pump.
Then we might conclude that we want something with wide dispersion that matches or is just below the power at the spraybar better control or maybe we can add another line to the pump so that it can deliver co2 directly.
Getting into the minutiae of these tiny decisions are what makes the difference between a pro tank and an amateur tank.
But I would like to do is propose a process that's just a bit more methodical as it can be helpful when our instincts don't produce the desired results. It's something I go through many times myself when fine tuning a tank, especially if I'm stuck with a certain aesthetic and don't have the flexibility to add more equipment or change flow direction. It can also help when extra fine tuning is needed later when plant mass changes.
So after thinking about how co2 interacts with the boundary layer in the tank, we can look at what kind of pump action we want. Do we want the pump to a) increase dwell time, b) deliver co2 somewhere specific or c) create turbulence? In this particular case we would want a) because the spraybar at the back is delivering even co2 across the width of the tank already along the surface to the front. Setting these objectives is really important because they can be different for each tank.
So the analysis would run something along the lines of: For a) we want something that can force fine bubbles deep below the tank and b) could be difficult because a pump itself is not providing any co2 because it is just moving water and we probably don't want c) it it drives out co2.
So for pumps we have to be much more sensitive to how it interacts with current from the spraybar and hard to get right even for experts, especially if it has limited flow power adjustments and narrow dispersion for the tank's configuration.
And the consideration of various solutions might involve: a) recognising that multiple smaller pumps might produce more evenly distributed power but the dispersion needs to be wide enough: b) considering whether wavemakers make things even more complicated and hard to control due to the eddies they create; c) evaluating whether the available pumps have sufficient control options d) looking at the type of nozzle - e.g should we use a normal nozzle, flat tip or wavemaker; e) exploring all available options - might a diffuser be better (especially if it's just one spot that Co2 is needed f) what about strengthening the filter pump or if not possible, g) supplementing it with additional atomisers, this quite common for weak filters?
Pump nozzle / output options
Non co2 injected pump configuration options:
These are just examples of things to consider before just reaching for the nearest available pump.
Then we might conclude that we want something with wide dispersion that matches or is just below the power at the spraybar better control or maybe we can add another line to the pump so that it can deliver co2 directly.
Getting into the minutiae of these tiny decisions are what makes the difference between a pro tank and an amateur tank.
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Hi,
Yes this is reasonable. Sometimes economics plays a role as well which may hinder some options. In any case, I don't think life has to be so complicated all the time if we are able to stick to the fundamentals. As noted in our sticky, we suggest spraybars mounted close to the surface facing horizontal and enough muscle from the filter(s) to push the water down to the substrate level. The diffusion technique also has to be excellent. An inline device works best and it must produce very fine bubbles. If the bubbles are even slightly large their buoyancy allows them to escape to the surface against the downward push of the filter flow, so many of the bubbles will fail to reach the plant beds. This is just our basic blueprint which we can deviate from as the configuration of the tank varies. Wavemakers and other adjuncts become necessary when the fundamental property of the filter do not meet the most important criterion - throughput.
Cheers,
Yes this is reasonable. Sometimes economics plays a role as well which may hinder some options. In any case, I don't think life has to be so complicated all the time if we are able to stick to the fundamentals. As noted in our sticky, we suggest spraybars mounted close to the surface facing horizontal and enough muscle from the filter(s) to push the water down to the substrate level. The diffusion technique also has to be excellent. An inline device works best and it must produce very fine bubbles. If the bubbles are even slightly large their buoyancy allows them to escape to the surface against the downward push of the filter flow, so many of the bubbles will fail to reach the plant beds. This is just our basic blueprint which we can deviate from as the configuration of the tank varies. Wavemakers and other adjuncts become necessary when the fundamental property of the filter do not meet the most important criterion - throughput.
Cheers,
Easternlethal
Member
Its not really all that complicated and growing to love these details is part of the journey imo
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