bio media - does slower flow rate give better filtering
- Thread starter mystic.bertie
- Start date
Himystic.bertie;2470818; said:
Just to clear up a couple of things. There have been studies done on hydraulic loading (flow rate across a filter) and it was found that the nitrificatíon rate increases with increased flow rate. Nitrification isn´t however the only important aspect when considering a filter. The mechanical filtration improves however, when the flow rate is reduced. This is because the water will be better polished at slower flow rates. You need to make sure you find a balance.
Just to clarify though you will not need a faster flow rate for successful nitrification in your tank. The bioloading on most aquariums (yes also monster tanks) never really stresses a well laid out filter. As a comparison some aquaculture recirculating systems run up to 60kg fish per 1000L/250gal water volume. These systems need high flow rates across the biofilter!
What does this mean for your canister filter? I tend to agree with others in this thread and would say you are better off running the canister at 600lph as the nitrification rates should still be fine but your water will be polished better. If you are still having problems with water quality visually then you may need more mechanical filtration. I find the powerheads good because through the current they produce, fine particles will often clump together and can then be more easily romoved through the filter. A good addition to the canister filter in my opinion.
j<><
With a lower flow rate the bacteria will actually have less time to 'eat' the ammonia because when your tank is operating as it should be, near 0 ppm, total ammonia is scarce and more flow pushes more water past the bacteria, feeding them better. They need no time to 'grab it' as it works by a process of diffusion. Low flow is bad.
goodness conflicting thoeries here 
maybe we need to see some tests that have been done, something not too scientific that we can understand
maybe we need to see some tests that have been done, something not too scientific that we can understand
Flow Rate (volume of flow) is one thing, Flow Velocity is another.
What you said doesn't work on all tanks and filter setups. Depending on the filter design, a high flow rate will increase the velocity of flow (obveously) BUT, when does the velocity start to be to great? No one really knows, the fact is that when the velocity is to great, the bacteria will NOT be able to eat up the ammonia as quick, possibly reducing the amount of ammonia the bacteria can consume per hour. This could also increase the cycle times.
In very heavily stocked tanks with a very large bio load, you will need a lot of flow to increase the water exchange rate but you will also need a LARGE bio surface area when doing this. Take the AC110 for example at 500 GPH compaired to the 550-600 GPH Fx5. The Ac110 has less than .5 liters of bio media. The Fx5 has over 5 liters of bio media running a a slightly higher rate. If both were running the same flow volume, the Fx5 would dominate the AC110 in ammonia consumption per hour. Slow the AC110 down to maybe 250-300 GPH and the AC110 may be able to consumer the same PPM of ammonia per hour the Fx5 can consume. (This is assuming they are on tanks of the same small bio load.)
600 Gallons per hours (flow volume) in a wet dry with a LARGE cross sectional and total surface area is completly different than 600 GPH in a canister which usually has a smaller cross sectional and total surface area.
There is a point when to much flow for the filter unit is bad for bio filtration.
This is not true. Yes your tank will be near 0ppm for ammonia which is good. That doesn't mean you have ZERO ammonia though. Those little test kits we buy are not that accurate nor are your eyes that accurate to the color of the test.
Your bio media has only the ammount of bacteria your tank needs for the bio load its producing. Slower rates mean the bacteria have more time to consume the ammonia and nitrite. When your is in the cycle stage, your bio filter media will have lots more bacteria on it than when the bio load is stable at a lower PPM. After cycling, you will have less active bacteria unless the bio load in the tank needs more.
Wrong. Bacteria are not people. They do not have arms. They do not need to catch thing. It works by diffusion. Reducing the flow rate on the AC110 you mention would only reduce the rate of nitrification.
Anyway, here is a link that talks all about it. Two of the articles are good, read both; the second one from the top and the fifth page of the article at the very bottom.
http://tinyurl.com/6g6ech
Anyway, here is a link that talks all about it. Two of the articles are good, read both; the second one from the top and the fifth page of the article at the very bottom.
http://tinyurl.com/6g6ech
Every thing I read (from the links you provided from the search) all talk about oxygen and nutrients and bio film. They all say that you need to run at maximum flow (of the filter). They also say that a higher flow rate, within limits, is better. I agree.
You run to slow, you will not have a very efficient filter due to oxygen and nutrient levels, run a optimal flow rate, you will have good bio performance, run TOO high of a flow rate, and you will be doing more harm than good.
Did you ever read the comparison between the Ehiem 2080 and the Fluval Fx5? The Ehiem 2080 pro3 has a tested flow rate of 318 GPH where the Fx5 has a tested flow rate of 600 GPH. The Fx5 has a 6" diameter round column full of bio media equaliing to 5 liters which will have a flow velocity of 1.36 inches per second. The 2080 has a larger diameter sqaure column (don't know the dimentions) equaling to 12L of bio media. The Fx5 at 600 GPH will have a much higher flow velocity through the bio media than the 2080. I'll quote from that thread;
http://www.discusforums.com/forum/viewtopic.php?t=7080
According to this, a higher flow rate is not always best. The 2080 has a slower flow rate over a larger surface while the Fx5 has a higher flow rate over a smaller surface which increases the velocity of flow faster than the 2080. Meaning, faster flow is not always better.
According to you, if everyone could run 1500 GPH through their filter that is rated for 280-480 GPH, that would be better.
Your right about the bacteria no having "arms". I never said they did, but if water with toxic ammonia comes screaming by the bacteria, its not going to be converted into nitrite and eventually into nitrate.
Now, what no one has been able to prove, is how much contact time is good and how much is to much.
To clarify,
a comparison of cycling times between different canister filters has more variables than just water flow ie type of media used, internal filter structure, filter material cross section etc. This means that no direct correlation between flow rate and cycling is possible in this case. The eheim may have been better but possibly for other reasons.
In scientific studies (no I can´t source them because i last saw them 10 years ago while studying) which I have read, the increase in nitrification didn´t slow down with extremely high flow rates (much higher than we are talking about here).
My personal experience is with many different types of filters but the highest flow rates i´ve used on trickle towers was 150 000L / square meter cross section. For a trickle filter under an aquarium with a cross section of say 40x40cm (~16x16 inch) that means a flow rate of about 24 000L (~6350 american gal) / hour.
For a comparison with filters with immersed filter material, I´ve run rapid sand filters as biomechanical systems with flow rates of 100 000L / square meter cross section. For an Fx5 (not sure of exact diameter - I used 30cm/12 inch) this would mean about 7000L (~1850 gal) / hour
What this all means is an ac110 for instance is biologically more efficient when running with a higher flow rate. The same applies for almost all types of biological filters (rotating biofilters may not work properly if flow is too high and fluid bed filters have set limits according to media size).
But the visual quality of the water is better if the cross sectional flow rate is slower across the mechanical filter due to water polishing (flow rates should be above where widespread anaerobic filtration occurs - may be dangerous).
Mystic.bertie, just to keep things in perspective I also have the largest model from the old eheim canister filters running at home (only filter on the system- see pic) and have experimented with different flow rates. The pump is an eheim 1262 with a maximum listed flow rate of 3400lph (900 gal/h). I get about 3000lph (790 gal/h) using larger tubing diameters. I have tried differing flow rates down to about 1500lph (395 gal/h) and haven´t noticed any difference in nitrification rates. The visual water quality vastly improved though with lower flow rates. The fine mechanical filtration was filter wool in all cases. These observations also fit to my professional experience in systems of relatively low stocking density (most home aquariums).
j<><
a comparison of cycling times between different canister filters has more variables than just water flow ie type of media used, internal filter structure, filter material cross section etc. This means that no direct correlation between flow rate and cycling is possible in this case. The eheim may have been better but possibly for other reasons.
In scientific studies (no I can´t source them because i last saw them 10 years ago while studying) which I have read, the increase in nitrification didn´t slow down with extremely high flow rates (much higher than we are talking about here).
My personal experience is with many different types of filters but the highest flow rates i´ve used on trickle towers was 150 000L / square meter cross section. For a trickle filter under an aquarium with a cross section of say 40x40cm (~16x16 inch) that means a flow rate of about 24 000L (~6350 american gal) / hour.
For a comparison with filters with immersed filter material, I´ve run rapid sand filters as biomechanical systems with flow rates of 100 000L / square meter cross section. For an Fx5 (not sure of exact diameter - I used 30cm/12 inch) this would mean about 7000L (~1850 gal) / hour
What this all means is an ac110 for instance is biologically more efficient when running with a higher flow rate. The same applies for almost all types of biological filters (rotating biofilters may not work properly if flow is too high and fluid bed filters have set limits according to media size).
But the visual quality of the water is better if the cross sectional flow rate is slower across the mechanical filter due to water polishing (flow rates should be above where widespread anaerobic filtration occurs - may be dangerous).
Mystic.bertie, just to keep things in perspective I also have the largest model from the old eheim canister filters running at home (only filter on the system- see pic) and have experimented with different flow rates. The pump is an eheim 1262 with a maximum listed flow rate of 3400lph (900 gal/h). I get about 3000lph (790 gal/h) using larger tubing diameters. I have tried differing flow rates down to about 1500lph (395 gal/h) and haven´t noticed any difference in nitrification rates. The visual water quality vastly improved though with lower flow rates. The fine mechanical filtration was filter wool in all cases. These observations also fit to my professional experience in systems of relatively low stocking density (most home aquariums).
j<><
