Hi all,
Lol kinda beats the point of an external filter though surley? I a, aswell use power heads and an air driven sponge filter, why would I buy externals to then have them empty?
They don't have to be empty, you can fill them up with media if you wish, just as long as it doesn't impede flow too much.
I have any combination of Eheim "coco-pops" , alfagrog, floating cell media, PPI10 sponge, glass rings, ceramic rings, hydroleca, pumice in mine, anything will do as long as it doesn't clog easily.
The really important factor, that is virtually never discussed on forums, is that once the water is in the filter you can't add any more oxygen to it, this means that it must have enough oxygen already present in the tank water to convert NH3 > NO2 > NO3.
If you look a conversion process we've added 3 oxygen atoms for every molecule of nitrogen, and we've liberated 3 H+ ions (which is why nitrification reduces pH).
People do horrible things with their external filters, they use them as syphons and stuff them with mechanical filter material like floss.
The end result is that the vast majority of the filter media is anaerobic, and although it
might contribute to the anaerobic de-nitrification of NO3, it doesn't contribute to the biological filtration process.
All you need to remember is that, when
oxygen supply exceeds oxygen demand you need a relatively modest amount of filter material for nitrification to occur.
The pre-filter sponge has 3 roles:
- It has access to the oxygen in the tank water (and evolved oxygen bubbles may adhere to its surface), meaning that it is a primary site for biological filtration.
- It stops debris getting into the filter, and
- It is quick and easy to clean, meaning that the filter is likely to run more efficiently.
There is more in these threads <"
Biological media please help">, <"
Recommended Filter Media">, <"
Canister filter">, <"
New filter media question"> & <"
Filter maintenance">.
cheers Darrel