A really good one:
how biological filtration works
(or, the enlightenment of poo and its eventual transformation into a new state of being)
Many people get into fish-keeping only to realise that they got into a hobby which is actually a lot more complex than they realised ... they lose a lot of fish by not understanding, not having any help and not having any basic sources to draw from. In the process they may lose a lot of fish, often expensive ones, freak out, tear their beards, gnash their teeth, yell about what a pooey hobby fish-keeping is ... and, disappointed, give it up ... which is always a great loss to the fish-keeping community. Biological filtration is the most grassroots principle in fishkeeping, and without doubt the most important to understand.
The vast majority of filtration systems in aquariums utilise biological filtration as their mainstay of converting harmful waste products into less harmful ones, however, there are certain conditions in which biological filtration will not work, which we will get to later. In tanks which house discus, the conditions will be ideal for biological filtration. The PH is around 7 and the water quite soft.
When setting up a new tank, a running-in or "cycling" period is needed before introducing its occupants. This generally takes 4 - 6 weeks.
Here's why:
When a new system is ready to start there are very few microscopic organisms living in it. Usually we use tap water which has been chlorinated, and a lot of bacteria and micro-organisms die from chlorine/chloramine poisoning, including those which are active in biological filtration (poor suckers, but lucky for us it kills he nasties, too, although, who knows what the chlorine does to us!). Thus the tank is quite sterile.
The Nitrogen Cycle utilises two species of bacteria, which will form in sequence as the system begins to cycle. The first of which to appear is the Nitrosomona bacteria. Fish generate waste which is quite high in ammonia content and the first stage in biological filtration is for the Nitrosomona bacteria to consume the ammonia and convert it into nitrites. This very important, because ammonia, even in relatively small concentration is quite a deadly substance for your fish. Nitrites, are somewhat less toxic, but are still very dangerous. It takes about 1 to 3 weeks for this to begin to happen effectively, but it doesn't finish here.
This is where the second stage of your biological filtration will come in. The second stage of biological filtration will kick in once there are enough nitrites present for our second type of bacteria to thrive on. These hard little workers are called Nitrobacter. Nitrobacter consume the nitrites and convert them into relatively harmless nitrates. This process takes another 2 to 3 weeks to occur naturally.
Both these bacteria are of a type called "aerobic" ... which doesn't mean they dance around a lot and play silly music ... it does mean that they need oxygen to function. There are many different ways to oxygenate your water effectively, but that's another subject.
Traditionally, a couple of cheap fish (guppies, feeder-goldfish) can be used to start the Nitrogen Cycle, utilising their waste products, however there are some enzyme based products available which can be used to "kick-start" this cycle and with these methods the cycle time is cut down quite a bit. Here is a good link if you want to learn about fishless cycling :
www.discusforums.com/forum/viewtopic.php?t=895 Another method is to use some of the media from an already established filter. Lucky you, if you have multiple tanks or a friend who will give you some established filter medium ... but be quick, in getting this into your new set-up, as the bacteria will begin to die within 1 - 2 hours, unless kept moist and in contact with air.
In nature, the end product of all this hard work are nitrates. Plants use nitrates in their growth process, and heavily planted aquariums with very few fish in them can be balanced, where the plants use all the nitrates present in the water. This isn't practical in most discus tanks, however, as many are bare bottomed, have no plants and have too high a population of fish for this to be a viable thing.
This is why we do water changes, often and conscientiously. Although nitrates are a lot less toxic than nitrites or ammonia, it still builds up and can pose a problem to fish, especially to fish like discus. So change your water, your fish will love you for it and smile whenever you come into the room ... I promise ... and just maybe they will dance
Examples of filters using biological filtration include under-gravel filters, fluid-bed filters, canister filters, hang-on filters, trickle-filters, sump filters, sponge filters, box filters, top filters, power filters etc, etc
As mentioned earlier, there are conditions of extremes where biological filtration becomes non-functional, as the bacteria cannot survive. One such instance is the kind of condition in which blackwater fish, such as some Apistogramma species need to spawn. This water can be as low as 3.5 ph and have extremely low, if any, hardness. Some species come from water so soft, it rivals Reverse Osmosis filtered water. Such extreme acidity will not be conducive to the survival of bacterial cultures in a biological filtration system and thus .... back to many many water changes (did I mention your fish will love you for those? and maybe, if you're lucky, get the newspaper for you in the morning and your flippers, too! .... but you gotta be very lucky).
One word of advice, also on stocking your tank ... when the biological filter is set up, try not to dump 50 gillion fish into your tank at once, but increase the load slowly and steadily, as the bacteria need time to increase as the waste products increase.
- enjoy your fish...
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