Filter retension time vs. turnover rate

[Scorponok]

I was alluding to the point that perhaps a tank with two filteration systems working in conjunction being, one with high retention time for biological filteration such as sump, and one with high turnover rate for mechanical filteration such as canister or powerhead, would maximize your tank nitrification efficiency.

The argument about maintaining high turnover rate and keeping water parameters to zero makes this topic a moot point is not logical. It means you are wasting money on electrical bills by not being efficient in filtering process and wasting electrical power.

 

[dawnmarie]

The argument about maintaining high turnover rate and keeping water parameters to zero makes this topic a moot point is not logical. It means you are wasting money on electrical bills by not being efficient in filtering process and wasting electrical power.

I'm not sure if I could put it better if I tried.
I may have to borrow this quote.

How many people do you suppose actually read completely the link you posted ?

 

[justin guest]

I like this, some good points have been made.

More practical applications? How about an amalgamation of flow rate and retention time. I’ve experimented previously with extra pumps in a sump. Pumps that serve to return water from the final stages of the sump back to the initial stages. This happens while overflows are returning tank water to the sump, and the sump pumps are returning sump filtered water to the tank. You just need a bit of residual water in the system.

Two factors would bother me with such a system. Firstly there would be no gain in nitrification rates unless some nitrite was left over and secondly you are pumping water back through the filter with reduced oxygen unless a trickle filter is integrated in the sump.

Bio filters will treat basically the same amount of water in a given time regardless of retention time as long as the flow rate is not so fast that bacteria cannot attach to the media

I am yet to see a filter where the bacteria couldn't hang on. Take fluid sand filters for instance. They are constantly rubbing themselves clean but are bacterial workhorses.

yeah,

if the water is travelling at a lower velovity, contact time is increased

it the water is travelling at a higher velocity, contact time is decreased, but contact frequency is increased.

this increased velocity brings overall contact time back up to levels of lower velocity rates.

but if u have extra sump pumps to recirculate sump water in the sump, u increase contact frequency again do you not ??

Here the important factor is ensuring enough oxygen is present. Higher oxygen levels increase nitrification. Higher velocity (without filter internal recirculation) does however also increases nitrification rates due to faster delivery of ammonia to the filter. This usually only matters in intensive culture systems though.

I was alluding to the point that perhaps a tank with two filteration systems working in conjunction being, one with high retention time for biological filteration such as sump, and one with high turnover rate for mechanical filteration such as canister or powerhead, would maximize your tank nitrification efficiency.

The argument about maintaining high turnover rate and keeping water parameters to zero makes this topic a moot point is not logical. It means you are wasting money on electrical bills by not being efficient in filtering process and wasting electrical power.

Optimal nitrification rates are achieved by increasing turnover but in private setting this is seldom necessary. As already mentioned by others, nitrification also occurs in the tank. I'll stick my neck out and say you don't usually need a biofilter, only mechanical. careful though, a mech filter that isn't cleaned at least weekly becomes a biofilter. Exceptions to the no biofilter rule are heavily stocked bare bottom tanks.

In nature there are no overflows with trickle filters and return pumps. Bacteria in nature do however gravitate towards higher nutrient concentrations. When we install a filter we are giving the nitrification bacteria an optimal place to live where the nutrients come to them quickest. That's why we need to be careful when cleaning biofilters and explains why some believe a biofilter to be essential. A biofilter only represents the best place for bacteria to grow, not the only place.

Hence my argument is that mechanical filtration is the only factor that really needs to be considered in a hobby setting when considering turnover and retention time. If you have biofiltration that's fine but don't worry too much about ideal flow rates as nature has already developed bacteria that can cope with a wide range of conditions and flow rates.

The most robust environment for good nitrification is one high in oxygen. This is the most important factor to consider when setting up a biofilter. I believe you are wasting energy when you allocate a pump purely for biofiltration. Just allocate a bit of space for biofilter material in your mechanical filter setup or use a filter material that does both ie foam, and rinse carefully in aquarium water. I believe this to be the most efficient use of energy.

j<><

 

[12 Volt Man]

careful though, a mech filter that isn't cleaned at least weekly becomes a biofilter.

I would argue that even then, you have a biofilter.

the bacteria are quite sticky and are not easily rinsed away from the media.

if you have media in a system, you have nitrifying bacteria colonizing it eventually.

whether we want it or not.

 

[justin guest]

I would argue that even then, you have a biofilter.

the bacteria are quite sticky and are not easily rinsed away from the media.

if you have media in a system, you have nitrifying bacteria colonizing it eventually.

whether we want it or not.

Agreed if you are cleaning the mech filter in tank water but nitrobacter species are sensitive to temp change and chemicals, so cleaning any other way will most likely stop the mech filter's ability to convert nitrite to nitrate.

Nitrobacter have a longer cycling time than nitrosomonas species (which convert ammonia to nitrite for the uninitiated) so it's feasable that ammonia to nitrite conversion will occur in a regularly cleaned mech filter. i assume for arguments sake that effective biofiltration means the two stage conversion of ammonia to nitrate. this would mean that at least the second stage (nitrite to nitrate) would occur in the tank and not the filter.

j<><

 

[12 Volt Man]

true, but nitrobacter and nitrosomonas are not the only species of nitrifying bacteria commonly found in aquariums. there are others.

they are sensitive to temperature changes, but not that sensitive in that a rinse will kill them. unless it is very hot water and left to soak.

as far as chlorine goes, as I have posted in a few threads, quick exposure to chlorine/chloramine from tap water will not kill the bacteria on contact.

chlorine takes time to work.

for example, the exposure time typically used at the water treatment plant for exposing water to chlorine in the contact chamber is, at least in Ontario, 20 minutes.

granted, the higher the chlorine residual of the tap water, the faster the chlorine will be effective in killing the bacteria.

but for the chlorine to be lethal to the bacteria given a quick rinse, it would be far higher than the concentrations found in our drinking water.

this is part of why you can rinse filtration material under tap water and not have nitrite/ammonia spikes in your tank.

the point of all this is that, as I said, even a 'mechanical' filter rinsed weekly even under tap water will still act as a biofilter as far as nitrification goes.

 

[Scorponok]

I'm not sure if I could put it better if I tried.
I may have to borrow this quote.

How many people do you suppose actually read completely the link you posted ?

You can use my quote anytime. I'd be flattered.

 

[KaiserSousay]

For the most part, pretty interesting discussion.
Well worth the read.
Didn`t find any information that would make me change how my tank filters, or how I would set up any future tanks filtration.
Anyone, after reading the posts or links making any changes?
If so, would you share method and reason?
The links to Koi ponds and their requirements was a nice change of pace for me. I guess if I had a few thousand wrapped up in fish, micro-managing their environment would be more than just interesting.
Thanks for bringing this up and to those who kept it going.

 

[justin guest]

true, but nitrobacter and nitrosomonas are not the only species of nitrifying bacteria commonly found in aquariums. there are others.

they are sensitive to temperature changes, but not that sensitive in that a rinse will kill them. unless it is very hot water and left to soak.

as far as chlorine goes, as I have posted in a few threads, quick exposure to chlorine/chloramine from tap water will not kill the bacteria on contact.

chlorine takes time to work.

for example, the exposure time typically used at the water treatment plant for exposing water to chlorine in the contact chamber is, at least in Ontario, 20 minutes.

granted, the higher the chlorine residual of the tap water, the faster the chlorine will be effective in killing the bacteria.

but for the chlorine to be lethal to the bacteria given a quick rinse, it would be far higher than the concentrations found in our drinking water.

this is part of why you can rinse filtration material under tap water and not have nitrite/ammonia spikes in your tank.

the point of all this is that, as I said, even a 'mechanical' filter rinsed weekly even under tap water will still act as a biofilter as far as nitrification goes.

Does your contact time of 20 minutes only apply to sensitive nitrifying species or is that for general disinfection? Your other point about tap water similar in temp to the tank water not always killing the whole bacterial culture is correct but often a temperature difference of a few degrees can already cause problems for nitrobacter and other nitrite converting species.

My own practical experience has shown this to be the case. I have seen spikes in nitrite that lasted for 2 days after cleaning biofilter material under tap water similar to tank water temp. I don't believe the nitrobacter cultures are being completely destroyed in this case but a nitrite spike remains something to be avoided.

Unfortunately cleaning your mech filter regularly without seeing spikes in nitrite does not immediately prove that your filter bacteria are robust as you may already have a displacement of bacteria to the tank substrate. I'm not implying this occurs in your case if you are careful about washing your filter but that this may occur. Don't forget tap water is different from region to region and country to country. You may be having success but others may not.

Another issue is one of air contact with normally immersed filter media. I've found you only need to leave immersed filter media out of the water about 30 minutes to experience a nitrite spike afterwards. This usually occurs where the air temp is significantly different to the tank water temp. In a household with family such a scenario can occur quickly while just giving the filter a quick clean.

I try to stick to filtration principles that I know will hold true in most cases and while you may have success I still hold that a mech filter regularly rinsed under tap water shouldn't be considered as a biofilter due to possible bacterial culture instability issues.



j<><

 

[justin guest]

Thanks for bringing this up and to those who kept it going.

welcome to filterholics anonymous

p.s. I'm already in treatment... don't like the taste of the malachite green much though