Sorry GluonGirl but the surface available in a practical sense is not unlimited. The bacteria grow in a layer on a surface. The thickness of the layer determines how small a feature can be that will support that layer. If pores or other features are smaller than would allow the bacterial layer to follow the surface, the entire pore is a waste of surface area and should not be counted in the total. The bacteria will just bridge over that pore and it will not be used as a growth surface. Anyone that uses the total surface area of all the pores in a microscopically porous material is selling snake oil not a biofilter. Many, but not all, of the ceramic biofilters are sold on the basis of the microscopic pores in the ceramics surface. It is a demonstrable fact that the advertised surface area exists and is equally demonstrable that it is a meaningless number because it is unavailable to the bacterial colony as a growth surface.
proper flow rate for biological filtration
- Thread starter fwiffo
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Hi OM47,
I liked your post. Further to the 'colony' you refer to, I battle to rationalise the (reported) importance of the development of a bacterial colony's slime matrix, with the need to clean filters.
If we just clean with calendar regularity, do we optimise bio system efficiency?
Cheers
Greg
I liked your post. Further to the 'colony' you refer to, I battle to rationalise the (reported) importance of the development of a bacterial colony's slime matrix, with the need to clean filters.
If we just clean with calendar regularity, do we optimise bio system efficiency?
Cheers
Greg
Que
I wish I was a fish I wish.
I wish I knew how to take measurements of the bacterial colonies. I'd really like to know just how much of it is in the filter vs in the substrate, on the glass and on the plants. I'd especially like to know just how much less of a role the filter plays in a heavily planted tank as far as bacteria are concerned.
Q
Q
Since you asked.... (this will teach you he.. he... he...)
There are actually several methods for determining the number of bacteria that is in a sample.
Sampling any media is always difficult but remember you don't have to include every single bacteria from a given region. A consistent reasonable sampling across all treatments it required. To test the glass a cotton swab rubbed against a measured surface of glass would work. To test the substrate physical agitation with the addition of some salts may loosen the bacteria from the substrate. Even using a mild surfactant may be usable.
The most common, cheapest, but least accurate is to use growth media and serial dilution techniques to estimate the bacterial counts. To make my explanation easy lets say we sample 1 gram of a sponge. To that 1 gram of sponge we will at 9ml of buffered water this makes a 1/10 dilution. We can then put it in a piece of equipment called a stomacher (this beats the sample up to loosen the bacteria from the substrate). We will then use a set of 9 more tubes of 9ml of buffered water. So we tank 1ml of water from the 1/10 solution and add it another test tube of 9ml of buffer to make a 1/100 solution. We then repeat these steps to make a 1/1,000, 1/10,000, 1/100,000, 1/1,000,000, 1/10,000,000, 1/100,000,000 and 1/1,000,000,000 solutions. We can then take 1ml from each of these solutions and plate using a good very general bacterial media. We then incubate these plates at 25C until we can distinguish clear bacterial colonies (I'd say 10-15 days). We then count how many bacterial colonies are on the plate. We can skip all those with <10 or > 200 on them. This usually leaves only one or two plates countable. Then multiply the number of colonies times the dilution factor. So if we had 145 colonies on the 1/1,000,000 it would equal 145,000,000 bacteria per 1 gram of substrate.
The limitations to this method is sampling accuracy, whether the bacteria species will grow on the media, and the accuracy of the dilution.
Another method uses a machine that passes the buffered sample between two electrodes. The bacteria will complete the circuit and send a signal that can be counted. This works only if the sample is really quite pure because many different particles will complete the circuit.
Now if you have a lot of money that you want to throw at the project you can buy equipment that can detect bacteria by running them through a glass capillary tube. It then shines a focused beam of light through the capillary tube and detects the refracted light from the bacteria. This is highly accurate and much faster than the old dilution method. It can also differentiate between bacteria and other junk in the solution because of the way it refracts the light.
For anyone who read this entire thing, didn't you have anything better to do you fool?
no,didn't have anything better to do than stretch your brain, Iknow all that but NOW AND THEN in science someone Does build a better filter OR bomb from a simpleminded query...Not me,not you obviously, but who lurks innocently out there....?
I have 150gph on a 29 gal (through a sump with 10 gallons of scrubbies) and my ammonia is always 0,even when i dont change the water for a while or overfeed.
Its is a combination of factors that determines where and how many bacteria one may have in any tank.
1. The bacteria need food in the form of ammonia and nitrite.
2. The bacteria also need oxygen.
3. The bacteria live on hard surfaces, not in the open water.
The size of the bacterial colonies will always adjust over time, up or down, according to the available food source. Even when at a stable number, some bacteria are always dying off and others are reproducing. This is why adding a filter to seed it for use in a new tank does not create more bacteria, it just spreads the number you have over more areas. If you remove too much this way, the original tank may have a mini spike even though the new filter and tank may not.
Given the above, the largest concentrations of bacteria will occur where the most food and oxygen are available. Most often this in in filter media. So the volume of media is important but so also is the available surface area it exposes to the flow of water.
This is the porosity of the media. One would think the finer the pores, the greater the surface area and thus the better bio- media. This is actually not the case. There are all kinds of particles/solids in the water and they vary in size. So the finer the pores, the faster and easier it is for them to become clogged, and once clogged the flow stops there and bacteria can't survive.
The problem with a lot of the bio-media out there is it is very fine pored and over time and despite regular rinsing, it clogs more and more making it less effecitve sooner or later. This is why filter floss is such a great mech media but also such a poor bio media.
All this just to say I find sponges to be one of the most effective bio-media. This is particularly true in terms of cost combined with the fact that it also acts as a great mech media for larger partical removal. And they can be rinsed over and over. The best bio-media, imo, is one which will support a lot of bacteria without eventually clogging irreprably. It should not be over costly, should last a long time and be reasonably easy to clean and reuse.
As for optimal flow rate. Normally, slower is better than faster. A slower flow rate allows the water to be in contact with the bacteria longer. That doesnt mean a slow motion flow, but it does mean that a slower flow over a larger volume of media beats a faster flow over less media. This is the principle behind the bio-wheel design. It is also why UGF/RUGF work best with medium sized gravel 3-4 inches deep with a steady slow flow through it. Small gravel blocks flow and big gravel provides less surface area. This is the principle behind the trickle filter as well.
Phew...
1. The bacteria need food in the form of ammonia and nitrite.
2. The bacteria also need oxygen.
3. The bacteria live on hard surfaces, not in the open water.
The size of the bacterial colonies will always adjust over time, up or down, according to the available food source. Even when at a stable number, some bacteria are always dying off and others are reproducing. This is why adding a filter to seed it for use in a new tank does not create more bacteria, it just spreads the number you have over more areas. If you remove too much this way, the original tank may have a mini spike even though the new filter and tank may not.
Given the above, the largest concentrations of bacteria will occur where the most food and oxygen are available. Most often this in in filter media. So the volume of media is important but so also is the available surface area it exposes to the flow of water.
This is the porosity of the media. One would think the finer the pores, the greater the surface area and thus the better bio- media. This is actually not the case. There are all kinds of particles/solids in the water and they vary in size. So the finer the pores, the faster and easier it is for them to become clogged, and once clogged the flow stops there and bacteria can't survive.
The problem with a lot of the bio-media out there is it is very fine pored and over time and despite regular rinsing, it clogs more and more making it less effecitve sooner or later. This is why filter floss is such a great mech media but also such a poor bio media.
All this just to say I find sponges to be one of the most effective bio-media. This is particularly true in terms of cost combined with the fact that it also acts as a great mech media for larger partical removal. And they can be rinsed over and over. The best bio-media, imo, is one which will support a lot of bacteria without eventually clogging irreprably. It should not be over costly, should last a long time and be reasonably easy to clean and reuse.
As for optimal flow rate. Normally, slower is better than faster. A slower flow rate allows the water to be in contact with the bacteria longer. That doesnt mean a slow motion flow, but it does mean that a slower flow over a larger volume of media beats a faster flow over less media. This is the principle behind the bio-wheel design. It is also why UGF/RUGF work best with medium sized gravel 3-4 inches deep with a steady slow flow through it. Small gravel blocks flow and big gravel provides less surface area. This is the principle behind the trickle filter as well.
Phew...
