Marine water - technical items

Marine water technology

Technical features of a marine aquarium

A special light, flow pumps, a chalk reactor and a protein skimmer are those technical items which distinguish a marine aquarium from a freshwater aquarium.


The water in marine aquariums needs a blue tone to look like the sea. That’s why we use cold light colours for the lighting, see Light . For fluorescent tubes you should combine a cold daylight tube (e.g. JBL SOLAR MARIN DAY ) with a special blue tube (e.g. JBL SOLAR MARIN BLUE ). Put the daylight tube at the front above the fish and the blue tube over the background above the corals. The JBL LED SOLAR NATUR in combination with the JBL LED SOLAR EFFECT give an ideal light for a coral reef aquarium with a colour temperature of 7800 K when the JBL LED SOLAR EFFECT is set to maximum blue. Contrary to the common opinion that marine aquariums must be illuminated with 10,000 to 15,000 K, it is clear to the specialists that our corals always come from shallow depths and thus do not need such high Kelvin numbers! The reason is the "laziness" of coral collectors, who have no reason to collect corals from 20-30 m depth when they can get them all from the reef top at 3 to 6 metre depths (and often thanks to UV protection with stronger colours)! Metal halide lamps (HQI) produce a highly suitable light, but with it enormous heat with a high power consumption. Light your aquarium as strongly as possible! The corals will thank you with beautiful growth. It is pointless to light a marine aquarium EXCLUSIVELY with blue tubes! The corals do not live at great depths, but mainly between the surface and depth of 30 m.

If the aquarium is illuminated with fluorescent tubes, the JBL SOLAR MARIN DAY in combination with JBL SOLAR OCEAN BLUE ULTRA, 24-39 W (No EEL label required. Exemption according to (EU) 2019/2015 Annex IV 3. g) coral-zooxanthellae symbiosis.) would be a good choice. Fluorescent tubes are NOT inferior to LEDs in terms of spectrum! Only their light output is of course lower than that of LEDs.


Almost all animals have become accustomed and adapted to the prevailing currents in the sea. Thus you need to simulate currents in the aquarium with water pumps. The biggest problem with currents in the aquarium are so-called "dead zones". These are areas, e.g. behind a stone, where dirt accumulation occurs at the bottom. These bottom deposits reduce the redox potential of the water and can lead to smear algae. Taking the example of a stone, a dead zone forms on one side of the stone when only ONE flow pump is used. By using a second flow pump opposite, alternating with the other flow pump by timer, this dead zone can be prevented. Bearing this in mind, it’s worth reconsidering the flow direction(s) in the reef aquarium!

(Water) Pumps

The possible applications of water pumps in bio filters, as flow pumps and many other uses
Chalk reactors

Your corals (and the other animals) need larger amounts of calcium, magnesium and other trace elements for their growth. In your freshly prepared marine water these substances are available from the start but will then be consumed. You have only two options: you can supplement calcium etc., such as JBL CalciuMarin and JBL MagnesiuMarin or you can use a chalk reactor. Fill calcareous material (coral gravel, marble chips etc.) into the cylinder of the chalk reactor and let marine water run through it. Connect a CO2 system to the chalk reactor which reduces the pH level inside the reactor to about 6 by adding CO2. As soon as the pH value falls below 7 calcium components from the coral gravel/marble chips dissolve in the water and can be supplied to your aquarium water drop by drop. This is certainly the most elegant but also the more cost-intensive solution compared to JBL CalciuMarin .

Protein skimmers

The protein skimmer contains of a cylinder which is entered by your aquarium water. A pump or an air stone creates a lot of air bubbles inside the cylinder. If there is a water pollution in the form of protein compounds (from food, fish excrements etc.) the many air bubbles form foam which rises upwards in the cylinder. At the upper part of the cylinder is a collecting vessel for the foam. This way you elegantly remove the pollutants, BEFORE they can be biologically broken down in the aquarium. Now you just need to empty the foam collecting vessel regularly and to adjust the foam quantity properly every now and then. Disadvantage: protein skimmers don’t only remove pollutants but also valuable trace elements and vitamins.

Measurement of salt density (JBL hydrometer)

With the help of a floating spindle, the JBL hydrometer , you can see how much salt is in your water. Most marine animals are comfortable with a density between 1.022 and 1.025. See Thermometer . As the temperature has an influence on the density measurement, you can read the temperature in the JBL hydrometer. In addition to the temperature displayed, the JBL hydrometer has a correction scale which shows you that, for example, if the temperature is one degree below 25 °C, i.e. 24 °C, you have to correct the density reading downwards by 1: you read 1.024, correct downwards by 1 and get the correct value 1.023. If the temperature is one degree higher, you have to correct upwards by one: 1.024 plus 1 = 1.025.

Alternatively, the salt content can also be measured with a good refractometer. Here, a drop of seawater is dropped onto a glass and you look through the device. The density can then be read on a scale.

Partial UV-C sterilisation

Even when your aquarium is not overfilled, scientific studies tell us that the bacterial count in marine aquariums is about one million times higher than in the ocean. This "bacterial pressure" leads to a higher susceptibility to pathogens in fish, comparable to having four coughing passengers in a small Fiat Panda, as opposed to having one coughing passenger in a big holiday coach. Using germicidal UV-C radiation through a UV-C water clarifier ( JBL PROCRISTAL UV-C Compact plus 5 W ) actively reduces the germ load, reducing the bacterial pressure on the inhabitants and thus increasing the health of the animals. UV-C water clarifiers are devices which allow aquarium water to flow past a UV-C emitting bulb, by using a water pump ( JBL ProFlow u800 ) The burner's UV-C radiation kills germs in the thin layer of passing aquarium water, thus clarifying the water. It is important to adjust the pump capacity to the UV-C performance according to the packaging information. If the pumps are too strong, the water simply passes past the UV-C bulb too quickly and cannot be sterilized optimally. That’s why a suitable pump size recommendation is always given on the JBL ProCristal UV-C clarifiers.

Air pumps

For the air pumps you need pumps with high air output, such as the JBL PROSILENT a200 with one air connection or the JBL PROSILENT a400 with two air connections. The JBL ProSilent a range not only delivers high performance but is also very quiet when in operation! Air stones are often used in protein skimmers and wooden air diffusers ( JBL Aeras Marin ) are the most popular type. They produce very fine air bubbles over a long period of time, which are a basic element in maximum foam forming. After a while, ALL air stones become clogged, producing significantly fewer and often larger bubbles. Then at the latest they need to be replaced with new ones.


A filter has the same task in a marine aquarium as it does in a freshwater aquarium: it is there to remove turbidity and dirt from the aquarium so that they can be removed from the system during the next filter cleaning. When it comes to the size of the filter, the following applies in seawater: Better one or two sizes larger than recommended on the packaging for an aquarium size X. When equipping the filter, please note that there are some filter materials that are unsuitable for seawater. This is always stated on the packaging, at least at JBL.

Unsuitable for seawater:

  • JBL Tormec activ
  • JBL Carbomec activ
  • JBL NitratEx
  • JBL Clearmec plus

All other JBL filter media are also excellently suitable for seawater.

Many marine aquariums have a so-called filter sump, which consists of a tank located in the cabinet below the actual aquarium. The water enters the tank through an overflow shaft and is pumped back into the aquarium after passing through the filter materials. With such filter sumps it is very helpful if the water first passes through some filter floss (JBL Symec or JBL Symec XL) before the water reaches the protein skimmer and other filter materials which are often included. This filter floss can be visually checked for contamination and then replaced in a few seconds if necessary.

JBL offers large filter sponges that can be cut exactly to size and are absolutely water neutral (JBL filter foam blue coarse). We recommend using the coarse rather than the fine filter sponge here.

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