How to Make Saltwater for your Marine Aquarium

In this guide I have put together you will learn how to mix up saltwater for use in your marine aquarium. Without saltwater your fish, corals and invertebrates would not survive.

Created by David Coton on Friday, 3rd of January, 2014.
Updated on Thursday, 7th of December, 2017.

Marine Aquarium with corals and fish.

Saltwater is vital for marine aquariums, and one cannot be set up without it, this is something which puts many people off setting up marine tanks as they believe it's difficult but it shouldn't be.

You can mix saltwater up in the comfort of your own home rather than having to travel and purchase the saltwater from a local store, it's great that aquatic centres like ourselves can offer this option though as people may be too busy or need it urgently.

We currently offer three levels of salinity and these are 1.022, 1.24 and 1.026, something which we pride ourselves on, speak to our Aquatics team now on 0121 355 7701.

There are different salinity levels which people choose and this can also differ depending on the type of tank you want to set up or have. If you have corals you are going to need a slightly higher salinity level than fish only marine set ups.

Saltwater Mixing Equipment

Before you start mixing salt and water you're going to need a few things, I have compiled these into a list below and I will go into further detail about these items later:

  • RO Water.
  • Sea Salt.
  • Mixing tub or bucket.
  • Hydrometer or Refractometer.
  • Aquarium heater.
  • A powerhead, submersible pump or air pump with airstone.

Prepare a Mixing Tub or Bucket

What you will need to do first is to prepare a bucket or tub for mixing the saltwater, I'd advise you purchase a new one as this should only ever be used for this purpose as cleaning products or other solutions can alter the pH level of the water if they have been used in the bucket before.

Fill your bucket with RO water, this water has been through a Reverse Osmosis system which will have removed undesirable particles from the water. RO water is available from aquatic centres like ourselves or you can purchase your own Reverse Osmosis unit. Always use measured amounts of RO water such as litres.

Heat the Water and Start it Circulating

Heat the water using an aquarium heater, always place the heater into the water and leave it for around 15 minutes so that the temperature can equalise, switch the heater on after this time and bring the temperature to 25 degrees celcius, this allows the salt to mix more efficiently.

Place your pump, powerhead or air stone into the water and switch this on also, this will circulate the water which will mix the salt once you add it. I think you'll agree this is much easier than stirring it yourself.

Measure then Add Your Salt

Next will be your sea salt, this should be as high quality as possible as it is going to stay in your tank for some time, there are also some brands who offer salt with higher trace elements like TMC Pro Reef salt which is very beneficial to all creatures including corals in the aquarium.

Measure out your salt, if you want a level of 1.025 then you'll need 35g per litre with the TMC salt we're currently using, so for 20 litres you'll need 700g. Check individual instructions as you may need more or less salt per litre with other brands, any good manufacturer will list this on their packaging.

Once you have measured the salt to the correct amount needed, pour it into the already heated and circulation RO water. Leave this to mix ideally for 24 hours for it to fully dissolve, the heater and powerhead must stay on the entire time too.

Wait 24 Hours While the Saltwater Mixes

After 24 hours have passed and the water has mixed, use a refractometer or hydrometer to check the salinity of the water, hopefully it will read the level which you were aiming for, ours was 1.025sg (specific gravity)

If you have added too much salt then add small amounts of RO water and leave to mix until it reads the correct level and the reverse applies if there is not enough salt, add small amounts and leave to mix.

Visit our online Marine Shop today for all your saltwater fish, coral and aquarium needs.

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