If I can toss some other people's 2 cents in:
http
/www.aquariumfish.com/aquariumfish/d...788&search=
... Probably the biggest repository of helpful bacteria in your aquarium occurs on the surface of each piece of gravel. Each grain, though appearing smooth to the eye, is rough at a microscopic level, and thus provides a huge surface area for the growth of helpful bacteria. So, it follows that if you sterilize your gravel, you will destroy most of the biofiltration in your tank. Not knowing this, hobbyists sometimes remove the gravel for cleaning and have been known to boil it, scald it or (worst of all) use bleach or soap to sterilize the gravel. This is a huge mistake! It kills off the nitrifying bacteria and will allow ammonia levels to increase rapidly in the water. Gravel should never be cleaned with anything but plain, aquarium-temperature water. ...
... Safely Maintaining Filters
The most significant part of your aquarium maintenance is likely to involve the cleaning of one or more filters. Filters don’t remove waste — they just collect it. Nitrifying bacteria grow on every solid surface in the tank, including gravel, glass, plants, decorations and filter media. Indeed, most filters contain some type of biomedia designed to provide plenty of surface area for the growth of helpful bacteria. So, it’s best to take steps to preserve the bacteria on this media when possible.
Disposable Filter Media
Many filters use disposable media as a convenient way to clean the filter. When the media is dirty, you throw it away and replace it. Slide-in filter cartridges for power filters are the most common example. But every time you replace disposable filter media, you throw out the good bacteria living on it. This may or may not be a problem. It depends on how much biofiltration there is elsewhere in the tank. For example, in a heavily planted aquarium with a gravel bed, it is unlikely to be a problem; there will be plenty of nitrifying bacteria colonizing those other sites. It would be different in a bare aquarium set up for breeding, however. The filter media would be the main source of biofiltration in such a setup. ...
... One final tip for maintaining helpful bacteria is to not turn the filter off, except for maintenance, especially with a canister filter. Helpful bacteria require oxygen. If a dirty canister is turned off, the helpful bacteria will use up the oxygen and die. Because the filter is closed off from air, nitrifying bacteria will be replaced by anaerobic denitrifying bacteria, which do not need oxygen to break down waste.
These produce hydrogen sulfide and other toxic substances as a by-product. If you turn this dirty filter back on after having it off for a few hours, a day or a week, it may force poison into your tank. If you have a power outage, it’s a good idea to clean your canister filter before restarting it. ...
http/www.novalek.com/kordon/articles/bio..._filtration.htm
... These nitrifying bacteria in biological filtration and the aquatic nitrogen cycle are in the beneficial gram positive group of bacteria, and their presence is important to aquarium and pond keeping. These bacteria are harmless to the aquarium inhabitants, as well as to man, pets, and other life, and do not cause any disease problems. They like to stick to positively charged surfaces, such as glass, gravel, and other substrates, filter materials such as filter pads, activated carbon, ceramic Raschig rings (see Kordon Bio-Mech) and glass decorations. They do not thrive on plastic, such as used in filter balls, or on the walls of plastic aquariums, or on plastic decorations. In fact, for those aquarists wanting for some reason to keep these bacteria low in number, they only need to be sure that as much as possible everything in their aquarium is plastic.
Small numbers of these bacteria will come into the aquarium and pond on the surface of the fish, invertebrates, or aquatic plants, or through moist air, or in natural food. Also, these bacteria can be provided by commercial culture products (see Kordon Zym-Bac) or by introducing some gravel or filter material from a well established aquarium or pond which already has gone through the nitrogen sequence. A cubic inch of gravel or filter material per ten gallons of water is sufficient. Given an adequate food supply, oxygen and a suitable substrate, these bacteria will quickly spread throughout the new gravel and filter bed.
Nitrifying bacteria typically establish themselves on the surface of the gravel, the inner surfaces of the aquarium or pond, inside filter tubing, and anywhere else that has a water flow resulting in good oxygen levels. Keep in mind that the greater the number of gram-positive bacteria, the greater take up of oxygen from the water. Ample aeration is needed so that the fish and aquatic invertebrates do not suffocate. ...
http/www.lifeforceonline.co.uk/aquarium_substrates.html
... An aquarium substrate is the material chosen to cover the bottom of the aquarium. It can, depending on the system type, be for purely decorative adornment, it can be an essential additive needed to maintain the water chemistry or it can be a major component of the aquarium filtration system. ...
... (Mathematically a finer substrate is a more efficient biological filter medium as it has a larger surface area providing a greater area for colonizing by aerobic nitrifying bacteria. ...)...
http/ezinearticles.com/?Nitrogen-Cycle-A...s&id=328078
... Ammonia (NH4) is assimilated in more than one way. Plants (such as Hornwort) and algae can assimilate ammonia and ammonium directly for the biosynthesis. The remaining bulk of decomposed byproducts are utilized by bacteria in a process called nitrification. Ammonia does not last long in a healthy aquarium environment, fortunately. Nitrifying bacteria such as Nitrosomonas quickly break down ammonia into less toxic Nitrite (NO2). During this process, specific species of nitrifying bacteria strip the ammonium of its hydrogen molecules as an energy source. Oxygen molecules are then affixed to the stripped nitrogen, forming the oxide nitrite (NO2).
Another group of bacteria (Nitrobacter ) utilize the enzyme nitrite oxidase that is then responsible for converting nitrite into nitrate (NO3). This nitrate can either be used by plants as a nutrient source, or can be further broken down into nitrogen gas (N2) through the activity of anaerobic bacteria such as Pseudomonas . ...
... Nature can pack a lot of bacteria into small places, which is to the advantage of the aquarist. For bacterial growth, all that is required is ammonia and oxygenated water. This is the beginning of the nitrogen process and the growth of bacterial colonies.
Remember you need oxygen and a lot of surface area for bacterial colonies. Wet/dry filters, sponge filters, ceramic media, and loosely packed upper layers of gravel are all sources for bacterial accumulation. If there is not adequate surface area in oxygen areas of the filter media or gravel, nitrification will be poor. Water will follow the path of least resistance, so if your filter or gravel has a build-up of non-nitrifying bacterial slime or is packed to tightly, nitrification will not be achieved. Sponge Filters or Pre-Filters are an inexpensive filter medium for colonies of nitrifying bacteria. Wet/dry filters and live rock (in Marine Aquariums) are excellent sources of bio filtration in larger aquaria. Bio-Wheels are very popular, but in my tests in my maintenance business they are VASTLY overrated. They tend to accumulate hard water deposits and stop and even when they are working my tests have shown little difference in aquariums when they are removed as compared to sponge filters or wet/dry filters. Canister filters are also good sources for nitrification as long as the proper media is used (such as ceramic rings) and the media is not packed too tight and is rinsed regularly.
ENITRIFICATION:
Is the process of converting Nitrates (NO3) in to Nitrogen (N2), which is dispersed into the atmosphere. This process can take place in an environment without oxygen by anaerobic bacteria. This process is more common in Marine aquaria and takes place in fine #00 sand, , live rock, or “aquarium mud”. In freshwater aquariums this process often produces deadly Hydrogen Sulfide, but by maintaining an oxygen level above 1 ppm, this can be avoided. Plants roots are great for maintaining this balance of oxygen in the gravel for proper Nitrate removal
A thicker layer of coarse gravel utilizing a "void space" called a plenum is often used for Nitrate removal in Saltwater and even freshwater aquariums. These are not to be confused with under gravel filters. ...
I found these interesting, anyway, maybe somebody else will.
