How UV clarifiers work
A UV clarifier works against bacteria, viruses, other pathogens, fungi and algae. Because the UV radiation not can distinguish between individual types of bacteria all bacteria destroyed, which are sensitive to UV radiation. This includes the bacteria that break down pollutants.
Normally, however, there are enough of these bacteria in the filter, in the substrate, on plant surfaces, etc. These bacteria are affected by the radiation not reached.
Even if some of these bacteria are in the open water and are thus deactivated by the radiation, the remaining bacteria multiply quickly enoughSo that the total population remains constant. Too many of these bacteria in the open water would also lead to a water bloom and possibly even damage the fish.
In the aquarium, attached bacteria and free-swimming bacteria compete for nutrients. The larger the colonizable surface is with an optimal flow, the lower the number of germs in the open water. The microbiology then mainly takes place in the filter or on the plant. Nevertheless, fish spawn, fish larvae and fish are colonized by bacteria.
UV clarifiers influence the competition between attached and free-swimming bacteria in favor of the attached bacteria. At the same time they support the mineralization of dissolved organic substances. There is always a balance that also depends on the load on the pelvis.
UV clarifiers do not make the aquarium water sterile. The number of germs is kept within natural limits at most.
The swarmers of a single Ichtyophtirius pathogen can e.g. B. contaminate a complete 1000 liter aquarium. In nature, they are distributed throughout the vast body of water to the cube of the distance from the host. So the risk of finding a new host is relatively small.
Because the entire aquarium water is not constantly irradiated, but only the small part that is currently in the UV clarifier, UV clarifiers cannot prevent some of the swarmers from remaining in the aquarium. Despite UV clarifiers, the number of germs in the aquarium is probably still a little more than twice as high as in nature.
UV clarifiers therefore have a preventive effect by reducing the number of germs to about the natural level and reducing the risk of infection for the fish.
To be on the safe side, UV radiation should be avoided during the running-in phase. However, there should also be no fish in the aquarium during this phase, so that no pathogens have to be fought. Even if filter bacteria are added to the water, no UV clarifier should be used. The bacteria first have to settle down in sufficient numbers.
Filters with built-in UV filters – make sense?
Filter with built-in UV clarifier in 400 liter aquarium
Filters with a built-in UV filter are also gradually being offered. Like any accessory, these have advantages and disadvantages.
The advantages include easy installation, as there is no need to connect water hoses. The filters are therefore ideal for reducing the germ density in the short term.
Disadvantage, the filters are often offered in low strengths of 5-15W, so that these are not sufficient for larger aquariums.
This type of UV filter is therefore particularly recommended – if continuous use is not planned. Furthermore, many filters with built-in UV clarifiers offer the option of using them without UV clarifiers. The UV function can be switched on or off individually.
Installation of a UV clarifier
If possible, a UV clarifier should always be installed behind a filter in the water circuit. Otherwise dirt particles and deposits can reduce the effect of the radiation.
If no external filter is available, an indoor fountain pump can be used as the pump. A small piece of foam is placed in front of the pump so that coarse dirt particles are caught.
If available, a small internal filter can be filled with cotton and connected in front of the UV clarifier. Of course, a small external filter can also be used in this way.
Due to the design and the way it works, fish are not harmed under any circumstances because they do not come into contact with the UV radiation.
Intermittent operation of UV clarifiers
Should a UV clarifier run continuously or not?
Intervals recommended by aquarists
- The last 3 hours of lighting so there are fewer germs in the water at night.
- 3-4 hours a day against floating algae and 3-4 hours at night against parasites
- 4 hours at night 2-3 times a week
- 3 hours at night
Arguments for intermittent operation with no problems present
- The relatively expensive UV lamps can be used longer.
- The bacterial load is noticeably reduced even with interval operation.
- In continuous operation, the water is completely sterilized. The infection pressure is taken off the fish, but the resistance is also reduced. If pathogens have to be fought, a slightly active immune system works better than an immune system that is never called upon.
- If the UV clarifier only runs in the evening or at night, the fish have less stressful water during their night phase and can recover.
- The useful life of a UV lamp is approximately 8000 hours of operation. The switching frequency has no influence on this. Physically, the lamps last longer, but after 8000 hours of operation, the performance is 30% less.
- In continuous operation, the effect of fertilizers and vitamins is greatly reduced.
Arguments for continuous operation without any problems
- Even in continuous operation, the water is not completely sterilized.
- Compared to the original waters of the aquarium fish, aquarium water is extremely contaminated with germs, ie bacteria etc.
- Even with continuous use of a UV clarifier, aquarium water is still more heavily polluted than the waters of origin of the fish. The immune system can therefore not soften even with continuous use.
- Lamp life is reduced because the lamp is turned on and off more frequently. The electrodes get worse with every switching operation.
Arguments for continuous operation with existing problems
- UV clarifiers should only be used when specific problems need to be solved:
- disease treatment
- water turbidity
Then only continuous operation makes sense.
continuous operation and fish health
The germ load in the aquarium is practically always higher than in the areas of origin of the aquarium fish. Even with continuous use of large-scale UV clarifiers, experience has shown that the load in the aquarium is about twice as high as in nature. There is therefore no reason to fear that the immune system of the fish will be under-challenged.
Some types of bacteria, so-called decomposers, have specialized in digesting organic substances. They colonize any suitable substrate and secrete substances that dissolve this substrate. The bacteria feed on the dissolved substances.
The skin of the fish is also a suitable substrate for these bacteria. This is why bacteria constantly settle on the skin and damage it. The fish’s immune system is constantly fighting these bacteria and constantly repairing damage.
A healthy fish can cope with this even with higher germ loads. When a fish is weakened, it can no longer defend itself against these bacteria and damage. The reason for such a weakening can be additional bacteria that are specialized in this fish species and against which the fish therefore has less chance. These can be parasites that weaken the fish and at the same time make it vulnerable to other pathogens through structural damage to the skin. But there can also be deficiencies due to feeding errors or the consequences of unsuitable water values.
In many aquariums, several of these causes are present at the same time, e.g. e.g.:
- The water quality in the majority of aquariums represents a compromise.
- Forage quality and composition is a compromise.
- The composition of species and the stocking density in the aquarium almost always represent a compromise.
- For reasons of appearance, compromises are made in almost all aquariums.
Virtually all compromises are at the expense of the Pisces. As a quasi-compromise in favor of the fish, the number of bacteria etc. in the aquarium can be minimized with a UV clarifier in continuous operation, thus relieving the fish for the most part. For reasons of fish health, there are no objections to the continuous operation of a UV clarifier.
Strength and sizing of UV clarifier
UV radiation can inactivate vegetative and spore-like forms of bacteria, viruses, other pathogens, fungi and algae. i.e. they are killed or damaged in such a way that they no longer reproduce.
UV-C lamps are normally used in aquaristics. The wavelength of UV-C is in the range of 200 to 280 nanometers. The optimal wavelength to inactivate microorganisms is in the range between 240 and 280 nanometers. Radiation of this wavelength irreparably damages the nucleic acid in the cells of the microorganisms. DNA is particularly damaged at around 254 nm. Because DNA and RNA carry the genetic information for reproduction, damaging them can sterilize an organism.
Some microorganisms are able to repair damaged DNA when exposed to light of certain wavelengths in the range of sunlight. You can even reverse sterilization by UV radiation. However, this is only possible within a certain time after the damage, because DNA damage becomes irreversible over time.
Professional systems for UV disinfection are therefore built in such a way that disinfected water is not exposed to sunlight immediately after disinfection.
Microorganisms must absorb the UV radiation in order to be inactivated. Various factors reduce the effect of UV radiation:
- Chemical and biological deposits formed on UV lamps. More than 0.1 mg/liter of iron can e.g. B. lead to deposits on the UV lamp.
- Organic and inorganic substances dissolved in water
- The color of the water
- Dense accumulations of microorganisms
- Iron, nitrites, etc. can absorb UV radiation
Studies have shown that a low dose of UV radiation over a long period of time is just as effective as a high dose over a correspondingly short period of time. If microorganisms are exposed to UV radiation over a longer period of time, an equal proportion of the living microorganisms is always inactivated at equal time intervals.
The dose of a UV clarifier is determined according to the formula
D = I xt
calculated.
I is the radiance in mW/cm2.
t is the exposure time in seconds.
D is therefore the UV dose in mWs/cm2.
UV lamps from Philips have the following radiation density:
power in wattsRadiance in mW/cm291215143015
How long does it take to get irradiated with…