Hi all,
This is what puzzles me when using pressure filters and Co2..where does the aerobic bacteria get its oxygen thats needed to support a healthy biomass
It is from the plants themselves (via photosynthesis), but this is what bothers me about canister filters in non-planted situations (even though the owners aren't adding CO2).
Personally I would always have a wet and dry trickle filter given the choice, largely because of their huge gas exchange surface.
In planted tanks the situation is different, the plants themselves are both removing ammonia and CO2 from the water column, and adding oxygen via photosynthesis, and at the end of the photo-period the water is likely to be 100% saturated with oxygen.
Once photosynthesis stops, the situation changes and the plants become net producers of CO2 and consumers of oxygen. This is why it is safest to turn off the CO2 at night, mainly because of the "Bohr-Root" effect :<
Fish Respiration>.
Have a look a this thread <
Overnight CO2 | UK Aquatic Plant Society>
Another point is that I like a sponge pre-filter on all my filters, this has a number of advantages:
- It stops faeces and sand getting into the filter
- It provides some additional biological filtration,
- it is very easy to clean
- and it provides an extra browsing surface/ emergency source of rotifers etc (if you squeeze it out) for fry.
I also have 2 filters in all the tanks that are 2' an above, usually a maxijet and sponge or Eheim aquaball, and an (Eheim) external <
best filter for shrimp tank? | UK Aquatic Plant Society>. An additional advantage of a pre-filter sponge is that you can aim the bubbles from the maxijet venturi at the Eheim intake sponge and/or vice versa.
I want as much oxygen in my filter as possible, because the microbial conversion of NH3 - NO2 - NO3 is an oxygen intensive process:
NH3 + CO2 + 1.5 O2 → NO2- + CO2 + 0.5 O2 → NO3-
The ways of increasing oxygenation are basically by having a larger gas exchange surface (in something like a wet and dry trickle filter), increasing flow speed or adding oxygen via photosynthesising plants. Plants also offer the dual advantages of adding more sites for microbial action and removing NH3, NO2 and NO3 from the water.
An external power filter, containing a large volume of ceramic media or sintered glass, and with high water turnover volume (x 10 or more), may still be working at a fraction of its capacity, if the water is rapidly de-oxygenated during its initial contact with the filter media.
A larger volume filter will add more potential sites for biological filtration, but if the factor that is limiting nitrification is the oxygen supply, they will remain as potential, rather than actual sites. A filter which is extracting a large amount of faeces may become partially clogged, reducing flow and also essentially oxygen, with a “double whammy” as the bacteria degrading the organic materials now inhibit the nitrifying bacteria in the filter by competing with them for oxygen.
That is really why I like a pre-filter, it is easy to clean and it keeps everything other than the ammonia out of the filter.
Biological filtration is all about oxygen, and it was the problems that L number keeper were having with this issue which prompted me to write "
Aeration and dissolved oxygen in the aquarium" <
plecoplanet: Aeration and dissolved oxygen in the aquarium>.
cheers Darrel