The Salty Side: Saltwater Aquariums for Beginners

Water Storage and Mixing Containers for Saltwater Aquariums

When it comes to saltwater aquariums, you will be dealing with plenty of water.  The bigger the tank, the more water!  Below is what I use for water storage and mixing containers for my tank.

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RO Water Storage Containers

Instead of running RO water only when you need it, you can use RO water storage containers.  You will therefore have water ready for emergencies or when you need to top up your saltwater tank.  

How Many RO Water Storage Containers Should I have?

Well, that would all depend on the following:

Water Changes

You may decide to do regular water changes.  I personally do not unless there is a problem.  (You can read more about how and why I do not do regular water changes here.)

The maximum amount of water that should be changed is 10% of the total volume of your reef tank.  So, if you have a 300 liter system, then you should have 30 liters available for each water change.  


Evaporation will be harder to gauge until you’ve experienced it.  To give you an idea though, in a 300 liter aquarium, approximately 5 liters of water is lost per day.  You would therefore need to ensure that you have a minimum of 25 liters of RO water available every 5 days.  

This is also dependant on whether your reef tank has a hood (which minimises water loss) and the type of lighting you have.  Metal halides emit a lot of heat leading to further water loss, whereas LED’s play next to no part in evaporation.



Finally, emergencies!  You never know when you need that little bit more water available.  This can come in many forms!  A toddler putting yoghurt in the sump, an anemone finding it’s way into a powerhead, a mistaken overdose or perhaps levels that are higher than they should be, such as salinity. 

Always ensure you have water available for such an occasion.  


So, based on the above, for a 80 gallon (300 litre) system, I would recommend a minimum of four 5 gallon Hedpack storage containers (or three 25 litre storages containers) to hold RO water.

It is important to ensure that any water storage vessels you use conform to national and international foodstuffs legislation. This means that the water will not become contaminated which chemicals in the plastic itself.

They should be made from food grade HDPE (High Density Polyethylene).

How Long Can You Store RO Water for a Saltwater Aquarium?

The longest I have kept RO water in it’s storage container is around a month as it is used up within this period.  As long the container is food grade then I don’t see why you can’t keep water safely for a few months at least.

Containers to Mix Saltwater

When it comes to mixing your water, the last thing you want is any type of difficulty.  It needs to be large enough to hold a good amount of saltwater in, but not too large so you have difficulty moving it to the tank.

It needs to be easy to add your salt to and you need to be able to physically mix the water (I use a large plastic stirring spoon).  You also need to be able to place a heater in to warm the water.

As with the jerry cans above, these mixed water storage containers also need to be safe for foodstuffs.  This way you know they are safe for your aquarium.  

I use 7.8 gallon buckets which are not that difficult to haul around and my preference has always been to make up only 5.2 gallons of salt mixed water at a time.

When working out how many buckets you need to purchase, remember that you will need:

A bucket to mix at least 10% of your water volume ie. if you have an 80 gallon (300L) aquarium, you will want to change a minimum of 8 gallons (30L) tank water.

A bucket to remove syphoned water from the tank.

You can adjust the above to suit your tank and it’s volume.


Don’t underestimate the usefulness of jugs!  

I use 2 x 2 pint (1 litre) measuring jugs.  One is primarily used for topping up my RODI water reservoir while the other is used for salt water.

And most importantly, having my own jugs means I don’t get into trouble with my wife for using kitchen jugs!!

Other Uses:


I use them whenever I purchase a new coral or invertebrates. You can either place the bag into the jug, which will hold it upright, or put the coral or invertebrates directly into the jug.

The reason I prefer to use measured jugs for acclimation of corals is because you can treat the 1L of water with 8 drops of Coral RX Pro accurately before adding to my system.

You can read more about acclimating coral and invertebrates in this article.


Brine Shrimp Hatching

I keep a Mandarin Dragonet (you can read about feeding a Mandarin dragonet here) and hatch brineshrimp regularly. I syphon the newly hatched brine shrimp into a jug and pour them into the tank, leaving the casts behind in another container.

So there you have it!

You can of course use whichever containers you choose but the ones mentioned above are the ones I have bought and use regularly.  

Just remember to ensure that they are food safe so that you know they will not leach toxins which could end up in your saltwater aquarium and affect your livestock.  

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