Different Agents for different filtering modes??

[niru]

Hi All

as I understand, there are 3 filtering mechanisms at work: mechanical, chemical and biological. I get what each means and does..

What I dont get is all this talk about the need for different specialised media for each kind of filtering, as if they are mutually exclusive. e.g. mechanical is essentially a mesh of some sort to keep out big & small particles/detritus out. And so long as you have enough oxygenated water & good flow, biological & chemical filteration happens almost everywhere . The main thing to look for is that the effective surface area has to be large enough to accomodate adsorbing agents/bacterial colonies. But are these media mutually exclusive: wont chemical filter media also do biological filtering (& vice versa)??

So why do manufacturers advertise/emphasize them separately?? Is it a purely marketing gimmick, or theres something real behind it? And I am not talking of specialized materials for specific issues (e.g. activated carbon for removing medications etc.. even they should be doing biological filteration).

Would like to hear your views/opinions on this.

cheers
-niru

 

[ceg4048]

Hi niru,
Yeah it's mostly marketing, but some products are for real, like activated carbon, or Purigen. The thing is that supposedly, the specialized media is a lot less effective if it becomes clogged with detritus. So that's why the noodles and pads are to be employed to act as interference. But there's nothing wrong in having the filter 100% filled with activated carbon so that the lower portions block the dirt and get clogged, while the upper portions remain less dirty. Likewise, there's nothing wrong with having the filter 100% filled with noodles which will do the same thing and will harbor useful bacteria, but which can't do what activated carbon does. The penalty is reduced flow though, so it might be better to fill the filter with nothing more than alfogrog, foam, plastic beads, or even pot scrubbers, which will improve flow rates and will also do biological filtration.

It just depends on your objectives as well as the specific problems.

Cheers,

 

[dw1305]

Hi all,
This is a subject where companies tell you the most amazing amount of truths and half-truths to sell you.......

Bio-Chem Stars® provide a home for massive colonies of healthy and active beneficial nitrifying bacteria that rapidly develop and maintain a biological filter, thus establishing a healthy ecosystem in both fresh and saltwater aquariums. Space-age porous polymer allows for rapid transfer of oxygen and water. ........

I'll ignore chemical filtration, as Clive as covered that, and I'll ignore mechanical filtration as well, other than to say that you need an easily cleanable (ideally coarse sponge) pre-filter on all your filter intakes. The only other thing to say is that if you really want very clear water, a diatom filter, new filter floss or a very fine sponge (PPI30) will polish your water for the short amount of time (until clogging occurs).

That brings onto biological filtration, and this is the one that counts. Don't believe people who talk out anaerobic de-nitrification, and plenums etc. you need as much oxygen as possible reaching your filter material, which can be anything from nylon pot scrubbers to sintered glass. In is a canister filter, as long as the media doesn't clog, and reduce flow speed, enough microbial flora will develop to deal with huge bioloads. It is really down to budget then, Siporax or Substrat pro are great, but you can buy a lot of alfagrog or pot scrubbers for a lot less money.

That is why I have the mechanical/biological coarse PPI10 foam pre-filter which I clean regularly, it keeps bulky organic debris out of the filter and maintains high flow speeds.

If you were really serious about biological filtration you would have a planted wet and dry trickle filter (with hydroleca), as these are an order of magnitude more efficient than other filters, due to their huge gas exchange capacities and the plants access to aerial CO2.

cheers Darrel