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How a saltwater aquarium is created-Part 4: The initial water


The water in particular has a strong influence on the development of the planned marine aquarium. Since we often no longer have such clean water, the market offers reverse osmosis systems. These can be used to purify the water. However, there are also important things to consider here.

Our water has a nitrate value of 0.7 mg/l according to an online analysis by the waterworks (as of January 2018), and the phosphate value is not even given in the analysis. But since we don't want to rely on this, and since changes can occur at any time, it was clear to us that we needed an osmosis system.

Many of us cannot avoid a reverse osmosis system, at least not when the focus is on coloured corals. The reason is impurities in the water. After the video you will find some interesting facts about the functioning of a reverse osmosis system.

Video of the commissioning of our system with ultra-pure water filter:


Through Armin Glaser's lecture on the subject of osmosis systems at the „Fisch und Reptil“ trade fair, we were able to learn interesting facts about the subject. I would therefore like to give you a short summary of the lecture, especially with regard to performance, clean and waste water rates, pressure increase and retention rate, but also on the subject of silicate retention.

Most of us aquarists will use a reverse osmosis system. The reason is clear, the water quality is often not clean enough for the care of delicate and often colourful corals. No one wants to introduce nitrates, phosphates or silicic acid into the aquarium with the water. As is well known, nitrate and phosphate are formed by feeding and excretion of the fish all by themselves. Additional nitrate enrichment through water replenishment or water changes is therefore not desirable. We saltwater aquarists are regularly faced with the dilemma of introducing new water into the aquarium, whether through evaporation or through necessary partial water changes.

I personally know only a few aquarists who work successfully with tap water in the long term. Most of them are breeders or pure fish keepers. Allow me to give a small hint for those of you who maintain small nano tanks and often work with distilled water. It is a fallacy that distilled water does not contain any residues. Silicate in particular is often still detectable here. (personal information Armin Glaser, as well as own measurement). Just to be on the safe side, it is advisable to simply measure the distilled water used.


Before we present the construction of an osmosis system, a few basic thoughts on the subject. For an osmosis system to function properly, a certain water pressure is required. As a rule, 3 bar is sufficient. Since in German-speaking households a pressure of approx. 3-6 bar is usually available, it should only be necessary to use a pressure pump in exceptional cases. (so-called booster pumps). However, these are available from the trade should you need them. The more pressure, the better the clean-water ratio


How it works:

The output water is pressed against a filter material. The impurities remain in front of the filter and the water molecules pass through. On the one hand it produces a usable water (called permeate) and on the other hand 1 to 6 times the amount of waste water (concentrate). You can see that 1-6 times is a lot of difference, but that is really the case.  If you want to read more about this, you can use the link to Wikipedia. There, the topic of osmosis is explained in detail:


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danmojar on 20.07.18#1
Hallo Robert,

das Video kommt genau zur rechten Zeit. Wir nehmen auch bald wieder ein Becken in Betrieb und haben uns exakt die gleiche Osmoseanlage zugelegt. Wir haben uns auch schon überlegt wie die Membran eingebracht werden muss :-)

Vielen Dank für eure tollen Videos

robertbaur on 20.07.18#2
Hallo Daniel

das freut uns. Danke Dir :-)

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