Best Salt for Saltwater Aquariums

One of the most important things to get right in reef fish keeping is marine salt. In the world of reef keeping we are inundated with a plethora of products vying for our hard earned money.

These companies have become very adept at convincing us that we need something, or that their product is better than another. To ensure that you are not wasting money it is always best to look in the direction of the users themselves.

I have been a reef keeper for many years now and in that time have used both Red Sea Coral Pro Salt and Red Sea Salt. From my first plunge into the world of marine keeping I have always been very keen to ensure that my inhabitants are well looked after.

Having very little knowledge at that stage I naturally gravitated towards Red Sea, a big name in Reef Keeping. Now years on, I am happy to say that I have no reason to change as the quality has always been excellent. (I don’t get paid for saying that! It is genuinely the product I use.)

The ‘new’ Red Sea salt product on the market when I started was Red Sea Coral Pro Salt. My aim was to keep an SPS dominant marine tank and this new product seemed to be the go to choice. However, I settled on the original Red Sea Salt which I believe is the best marine salt for a reef tank.

Before I tell you why Red Sea Salt is my preferred product, it’s worth considering what you are trying to achieve by adding any salt product to your RODI water.

Natural Sea Water

The purpose of marine keeping for most reef keepers, apart from keeping beautiful fish and amazing coral, is to emulate the natural environment these creatures have evolved in.

There is far more than just plain salt dissolved in the water from which our fish and coral originate.

Therefore salt manufacturers have striven to reproduce what we find in the ocean. The salt content in any salt product you buy has less importance than the basic elements which create the balanced parameters in your aquarium as well as the trace elements mixed in with it.

The salt in the mix is there simply to maintain the salinity of your water.

In fact, salt is the only component in a salt product which is not readily utilised by your inhabitants. Having run a tank without water changes for years, salt is the one constant. It remains perpetually at the same level.*

On the other hand, the reduction in carbonate hardness, calcium and magnesium, as well as trace elements through uptake** is expected from your corals and invertebrates.

My leaning is towards maintaining the levels of my tank to those found in natural sea water.

The values above have been collated to present the similarities and differences between NSW and Red Sea salts. These give you a good indication of the offered parameters are for a reef tank compared to the ocean. These values are based on what is found in areas of the ocean where reefs are found.

With this knowledge at hand Red Sea Salt is a no brainer if your intention is to replicate the conditions found in the sea.

Your Little Bit of Ocean

I have already stated that I keep my tank as close to natural conditions as possible, however this has not always been the case. The environment you provide for your marine inhabitants comes down to your preference and what you want to achieve.

Referring to the table above again, you will have noticed that Red Sea Coral Pro Salt introduces raised levels of alkalinity, calcium and magnesium. The purpose of increasing the values in the salt mix is to encourage faster growth by providing an abundance of the required levels. 

Having used Red Sea Coral Pro for a couple of years I can testify that it is the best marine salt for a reef tank when aiming for faster growth, most notably seen in frags when freshly cut.

When I first started my 4ft tank off it was a typically coral-sparse rockscape dotted with small SPS frags of many varieties. Now although patience is the name of the game in reef keeping, if you want to encourage your corals to grow faster to achieve the scape you want there is no reason you shouldn’t. Having used Red Sea Coral Pro in my previous tank I decided to stick with Red Sea Salt.

I my experience, my first system seemed unable to maintain the Red Sea Coral Pro Salt levels at such high values. They frequently became imbalanced and I found myself adjusting dosages to compensate on a regular basis.

When I moved on to Red Sea Salt I found that the levels remained balanced. I was no longer fighting to maintain the higher values. My system seemed happier with less fluctuations.

Then when I  upgraded to my 4ft I stopped doing water changes altogether, but that is another article. Click here to see how I do it.


It’s worth touching on salinity while talking about salt. The two do go hand in hand after all. With any salt you buy, the salinity you desire will determine the mixing rate you use. The salinity in your system is primarily determined by water evaporation from your tank.

Most systems are maintained at a specific gravity of 1.025 or a salinity of 35, both of which are simply two different methods of measurement. From time to time salinity does need to be adjusted to your preferred level. It is always better to make the adjustment slowly rather than correct it as quickly as possible in a panic. This will cause stress in your tank to both your fish and corals.

If you are adding RODI water manually it is always good practice to check the salinity in your tank prior to water changes. This will enable you to adjust to the correct salinity prior to the water change. The addition of a water top up unit does make the world of difference in salinity management. In my eyes it is something I would never do without but it does require a system with a sump.

Check out my other articles for more information on evaporation and auto top off units.

*Wet skimming can reduce salinity over an extended period of time, as can bad management of RODI water top up.

**Uptake: the utilisation of elements and trace elements through absorption. 

What is the Best Salt For A Saltwater Aquarium?

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