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Comparison: Natural Sea Water VS Salt Mix

Comparison: Natural Sea Water VS Salt Mix

As seen in many online discussion portals, there’s a lot of debate about the comparison against Natural Saltwater (NSW) vs Salt Mix (SM) debating which is a better option. Today I’ll will try to share with you and break down the pros and cons between NSW and SM for you to decide which is more suited for your tank and why is that so.

Natural Sea Water

Seawater pack into 10L bag from Ah Beng Aquarium

Natural Sea Water (NSW) as the name applies, is collected naturally from the sea. usually, it involved a special vehicle that collected the seawater from one of the remote places of our shore and transported to the Live fish shop. As the natural seawater is dirty and could contain dirt, some form of preparation and filtration is required before it is put up for sales. The Live Fish Shop (LFS) will usually filter the raw seawater before selling it to you to make sure that the water is clean and to prevent unwanted organisms that might come along. MOST LFS will usally do a simple form of treatment and filtration themself which usually involves running the seawater through small micron filter sock , ozone and UV to sterlise the water before use.

Now let us break down to the Pros and Cons for easier understanding.


  • Natural Seawater (NSW) is “cycled” and ready to be used completely, as it usually contains live beneficial bacteria from the sea. However, if you’re setting up a new tank, the live bacteria that contain in the natural seawater will greatly help speed up the cycling time of your new tank.
  • You’re not required to put anti-chlorine for NSW (Never trust tap water, you never know what it contains) or use RO water to mix because it is already ready to be used right away.
  • It is cheaper to purchase as compared to buying salt mix. All you need is to purchase the NSW and use it.
  • It is simple and easy to use- No messy mixing of salt water or RODI filter required to prepare your water for saltmix.


  • If you are intending to store your NSW for future way, It required circulation else the live bacteria might die and this method could take up space as well to store it before use.
  • The parameter of NSW is not stable, as the salinity will vary between season and weather. Especially when collecting the seawater after a heavy rain, the salinity will definitely decrease. Our local Natural seawater range from 1.019 to 1.023, so topping up of salt is necessary to bring it up to the ideal level..
  • Naturally, a lower salinity could also mean lower parameters like low calcium, KH , mg etc… Which required topping up of these elements as well for a reef tank.
  • Although there might be some form of filtration carry out, there’s might still be a chance of parasite being introduce into the system if you are using NSW as it is not 100% filtered due to the large volume they handle.
  • Logistic wise, delivering NSW is a nightmare as just to imagine having to carry 10 bags of NSW back home for a major water change, so, all in all, it might not be cheap after all.
  • If you’re keeping a ratio of corals that depleting your elements faster than you replenish the elements, using seawater that has a lower parameter might result in your corals depriving the corals of elements example (CA, MG, KH). Which means you need to dose more of these elements, which add more cost to it as well.
  • unlike using a salt mix , If you are using NSW, you will not be able to know the water parameter of your batch of NSW that you are using, unless you tested it, and bare in mind each batch of NSW that you use the parameter might be different.
Various brand of saltmix ( ref; bulkreefsupply )

Now let’s talk about salt mix.

Video on how salt mix are produced.

The term salt mix simply means using aquarium salt to mix with your freshwater to produce synthetic saltwater that is suitable for both marine fish and corals. (Most of the time, we would recommend using a RODI filter to produce pure water which is free from any harmful impurities or substances which is often measured by TDS level. This would avoid adding any unknown source of the chemical into the salt mix that you are preapring.

A typical 5 stage RO/DI water filter

*Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water.

There are many various selling brands of salt mix available in the market, however, the prices of the salt vary from the country of origin, brands, parameters and weight of it.

Here’s the Procs and Cons of using Salt mix.


  • Control level of trace elements that you know what you are adding into your tank.
  • No unwanted parasite
  • Easier to store as you only need to take out and mix when needed.
  • No expiry date – Generally salt mix can be store for a long period of time without getting bad.
  • Might be cheaper comparing to NSW to produce more saltwater vs weight.


  • Need to mix and wait for the salt mix to be fully dissolved before use. BE PATIENT
  • Need to dose bacteria especially when using it on a newly setup tank. However, some new brand of saltmix come with bacteria in it as well.
  • Relatively expensive for small water volume change. (Unless you are buying in bulk)
  • Require you to invest in a RO/DI water filter unit for your saltmix.

To learn how to use salt mix with RO water, check the video below!

That is it for today’s articles. Both have its advantage and disadvantage but it all depends on what kind of system do you want to run in. If you are interested to know any topic feel free to let me know!

If you want a clean and stable parameter every time you do a water change, Salt Mix could be the best option for you!

To understand more about reef chemistry and how it affects our reef tank, you may read more about this article here.


If you want to establish your new tank fast or if you want to do a major water change without requiring the time to stabile the parameter, then you can consider using NSW since it comes with bacteria. However, if you are doing a water change to replenish your existing tank water parameter or if you are concern about the safety of the water then using a salt mix might be a safer option to go for.