Got a small tank?


I feel sorry for you, but only because you are going to have to be even more diligent than large saltwater tank owners…


nano tank

Mini tanks can be stunning, but you will need to pay them a lot of attention (photo credit: pinterest.com)

Saltwater aquariums of a volume less than 40 gallons are so popular at the moment (interchangeably named either micro, mini, nano or pico) , they get hyped as a cheaper, easier way to get into the saltwater hobby but are actually more challenging, more likely to crash and are not really recommended for beginners.

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A common mini tank scenario

Average Joe down the road buys into the hobby because he is attracted to the small capital outlay, plug and play-ability, portability and lack of space required with a tank volume less than 40 gallons. People like him are often are sold the concept as a pre set-up mini reef, the guy from the LFS says is “easy” to take care of because it is small and houses fewer species than a bigger tank.

But A few days, weeks or months later something goes horribly wrong with the mini tank and everything living is wiped out really fast.  Average Joe then gives up the hobby because of this fatal event that he wasn’t prepared for…

This illustrates two points:

  1. No-one should get into this hobby without taking it seriously and learning about all that is required for marine life support before they jump into the deep end, especially with a smaller tank.
  2. Small tanks are inherently unstable and require special treatment and more regular testing and monitoring compared to larger tanks.

The bottom line is a smaller tank is much less stable than a bigger tank in terms of degrading water quality in case you overfeed, something dies or the power cuts out. If you are contemplating a tank of 5 gallons or less, forget it, unless you really know what you are doing! Really, this minute volume of water gives you NO room for any error; a big risk especially for less experienced aquarists, leave it to the pros or the uneducated is my advice.


If you are a beginner you should always go for the biggest tank size you can afford

Larger tanks have more water so have a greater dilution factor or buffering capacity should something go wrong physically or chemically. You also have more time to react and correct the problem before marine life starts dying, which can happen in a matter of hours for a tiny tank.

Small tanks have a perceived low cost due to their size and people also think that they are easier to set up and maintain. But the truth is to successfully keep a tiny tank you are going to have to use a lot more skill and attention than you would a bigger tank.

But, don’t let me put you off tiny tanks; if you are diligent, do your homework and follow the recommendations I will make on this post there is no reason why a mini tank can’t thrive in your home.

A minimum saltwater aquarium volume of at least 40 gallons is my recommendation for the beginner saltwater hobbyist. Remember, the greatest number of saltwater aquarium quitters turn their backs on this awesome hobby because of a very bad tiny tank experience.

nano tank

A tiny tank gives you a very small window to respond before marine life starts dying (photo credit: Flickr.com)

Ten Tips to get your Tiny Tank Thriving

I hope I haven’t completely put you off small set-ups, it’s just that there are a few issues to be aware of regarding the limitations of tanks smaller than 40 gallons. If you are patient and your focus is on balance and a sustainable set-up there is no reason you can’t succeed.

Here are my nano tank tips:

1. Small tanks need species with low metabolisms and low activity levels to keep waste levels to a minimum, therefore there are less choices especially when you factor in species that will happily live with each other in such close living quarters.

2. Adequate biological filtration is obviously key for small tanks because of the urgency to get rid of ammonia, nitrites and nitrates in such a small, enclosed space. A hang-on power filter is a great idea, with plenty of bio-balls/other media for bacterial populations to colonize. Remember to change/clean filter media very regularly.

3. Using a small protein skimmer and some live rock is also a great idea, especially with nano-reefs. Using phosphate remover in the filter housing is also a good plan for reef applications thus keeping corals happy in a small space.

4. In terms of lights; less is more. Powerful lights like metal halides can very easily fry your livestock. In many applications normal output fluorescent bulbs will easily provide enough oomph for hard corals in such a small setting. Power compact or T5 lighting systems will be more than adequate for full blown mini-reefs. Heating of water caused by lighting is something to watch carefully, with such a small tank volume a fan directed at the back of the tank will usually take care of this.

5. Water changes of 10-15% per week must be done without fail! Cleaning up detritus will help the filtration out a lot. Evaporated water top ups are very important with such a small volume, displaced water plus heat from the bulbs can easily equal fish soup.

small aquarium tips

Stock your nano’s with peaceful, non-stinging species that will be happy living in close quarters. (photo credit: Flickr.com)

6. Test parameters like pH, temperature, salinity and nitrates regularly (like at least once a week). With small tanks the first indicators of something going wrong with be your sea creatures themselves, so observe your pets carefully every day.

7. Choose few specimens, as I said the less active the better (fish), non stinging (invertebrates) and species happy to be in close quarters with each other. Less metabolically active fish choices would be Clownfish, Hawkfishes, Gobies and Blennies which also eat less than more active fish.

8. Select non-voracious eaters: inverts and fish that require little, if any supplementary feeding are the best, so corals and sand sifting Gobies for example will be excellent choices.

9. Get a quarantine tank; disease can and will spread like wildfire in smaller set-ups.

10. Obviously a mini-reef set-up is going to produce less organic waste than a tank with fish. Consider getting some tank janitor species to help process waste before it hits your filtration.

Should you decide to try your hand at a tiny saltwater aquarium, don’t forget, patience, balance and a well thought out set-up will greatly enhance your chance of success.

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Andrej Brummer
Saltwater Aquarium Advice Scientist