Filtration is the process of removing undesired particles from a certain media. Unwanted elements in ponds include pond detritus, outdated fish food, dust, and other materials that may be in the water, the medium. This is known as “mechanical filtration” because it involves the mechanical removal of particles from water. But, probably more crucially, there is a chemical activity that must take place in a pond. It is the process by which nitrogen, which is produced as ammonia as protein decays, is transformed from deadly ammoniacal nitrogen (NH3, NH4) to plant-fooding nitrogen oxides (NO2, NO3).
As previously mentioned, this is just the removal of particles from the medium, water. This may be anything from a grate that collects tennis shoes and basketballs from municipal storm drain to ultra-fine filters that eliminate pathogens from water. An excellent pond filter is somewhere in the middle of these two extremes. People have traditionally used pool filters, which employ fine silica sand as a medium. This is fantastic in a pool, but in a pond, it rapidly clogs up and becomes more of a hindrance than a benefit. The modified pool sand filter was the next phase in the development of pond filters, in which the laterals were punctured full of holes, generally with a screwdriver, to enable greater flow, and the sand was replaced with lava rock. This is a highly successful strategy that is still extensively utilized today. The lava collects enough particles to be considered a reasonable mechanical filter, and it supports a huge bacterium population. There are several different filters available now for ponds of varying sizes and fish loads. Some utilize foam mats as the medium, which works well but rapidly clogs up, while others use different variants on the “bio-balls” motif, in which a plastic item with a huge surface area and plenty of open space is made to enable free passage of water. If properly managed, all of these things will give water clarity and a healthy pond.
It is less vital to remove particles from water than it is to process nitrogen, therefore if a compromise must be made, err on the side of biological. In other words, allowing particles of a particular size to escape back into the pond to convert a large amount of ammonia to nitrate is preferable to catching everything down to a micron or less and slowing the water down to the point where the bacteria have a difficult time thriving. The bacteria that accomplish this task for us belong to a kind of bacterium that we’ve all heard of before: “nitrogen-fixing” bacteria. This implies they absorb nitrogen that is inaccessible to plants in its ammoniacal state and convert it to an oxidized form. These are the same bacteria that dwell in leguminous plant roots. Life as we know it would end if these helpful microbes did not exist. So be gentle with your microorganisms. They want a vast surface area, a chemically inert substrate, and an abundant supply of fresh water. They rely on dissolved oxygen in the water to survive and perform their duties. When the water flow is interrupted, the oxygen in the filter becomes limited and ultimately depletes. The microorganisms eventually die, and you must restart from scratch. Some builders employ both mechanical and biological filtration, and some modern equipment does as well. In the first instance, many individuals are tempted to install a canister filter ahead of the lava rock filter, believing that by capturing all of the particles that would ultimately block it, they would prolong the life of the lava rock filter. They are accurate, of course, but in order to avoid damaging their pumps, which must work too hard to force water through the cartridges, they become slaves to the cartridge filters. It is preferable to just use the lava filter and keep it in good condition. Placing the canister after the lava filter is an excellent idea, however the same issue happens, although less often. You may now choose from a variety of microorganisms, each with its own specialization. It is critical, to begin with, a healthy supply of beneficial bacteria in order to avoid the green water stage of pond creation.
The notion is that passing the water through the UV bulb kills unicellular organisms, which is, of course, correct. It is used by many individuals to keep unicellular algae at bay. My attitude has always been that if the water is green, or wants to be green, there is an issue that can be dealt with more comprehensively than with a UV lamp. String algae, blue-green algae, and huge fish parasites are not controlled by UV lighting. Many people make the mistake of leaving their UV lamps on while attempting to kill string algae with live bacteria. UV lamps are best utilized in large groups of fish since they eliminate numerous tiny fish diseases such as “Ich” and fungus. As a result, having them on is particularly critical in the late winter and early spring months, when diseases are active before the fish are completely active.