Salty Q&A: Are Fish in Nanos More Likely to Leap?

Fish jumping issues in nano aquariumsThis question, recently posted on our website by Eric B, got me thinking about some of the assumptions we tend to make about nano aquariums. So, in addition to my original answer to Eric’s inquiry, I’ve included a few more random thoughts on the subject afterward.


Do you think that nano reef tanks are more likely to have fish jump from them, or is that not really a factor in your eyes?” – submitted by Eric B


I think as long as the fish in question is 1) an appropriate nano candidate from the standpoint of maximum size and energy level, 2) not crowded or harassed by tankmates, 3) provided adequate niches for rest and refuge, and 4) kept in good water conditions, there’s no reason it should be especially prone to jumping. Of course, these same caveats apply to fish kept in any system, nano or otherwise.

That being said, it is much more challenging to find fish species that are well suited to nano tanks than to larger systems. So I suppose one could argue that fish jumping is more likely to be an issue with nano tanks in general, merely because it’s all too easy to stock them inappropriately.

A few more thoughts

Building on this last point, it’s tempting to think that all bad things happen more rapidly or are more likely to occur in nano systems than in larger ones, but the reality of the situation is a bit more complex. It’s true that smaller aquariums are inherently less stable than larger systems with respect to temperature and other water parameters (which is why we don’t encourage beginners to start with nanos); however, I believe success or failure with a nano tank ultimately comes down to maintaining a sense of proportionality.

What do I mean by this? By way of explanation, let’s consider dissolved pollutants. This level is no more inherently prone to rising precipitously in a smaller aquarium than it is in a larger one. In other words, a proportionately stocked and judiciously fed nano is no more prone to an excessive level of dissolved pollutants than is a proportionately stocked and judiciously fed larger tank. It all comes down to nutrient import versus export, which is largely within the hobbyist’s control. No matter the size of the system, we have to strike the right balance between the stuff that goes in via livestock additions and feeding and the stuff that comes out via skimming, filtration, water changes, etc.

So, many of the admonitions against nanos really have more to do with human nature than problems inherent with the systems themselves. It takes a high degree of discipline to limit the bioload in a nano tank to the level it can reasonably support, and not all of us have that. Heck, I’m pretty sure I don’t have it!


If you enjoyed this post, subscribe to get our new posts in your email.
About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. Fish as with any animal need to feel safe and the environment as with the reefscape needs to suit the fish we keep. A single specimen that in nature is found I pairs or groups is more likely to feel insecure in it’s surroundings. IMO a happy fish is less likely to jump.

  2. I’m pretty excited my comment on your other post inspired you to write this post. I’ve always had at least one nano reef set up since I got into this hobby, but I’ve always had a lid because I’ve been afraid of a fish jumping. I do have a wooden canopy with vents on my current tank, which still allows for some gas exchange like an open tank, but I’ve always been envious and fearful of open top tanks. Maybe I’ll give it a shot in my next tank build. 🙂

    • It’s our pleasure, Eric. Thanks for posting the question. I’m always reticent about going with an open top too, especially when a fish is newly introduced and really skittish. In some cases, I keep the tank covered just for the first week or so while the newcomer gets settled in. Jumping is still always a possibility, but once fish get settled into their own niche and establish a regular hiding place, there’s a better chance (though no guarantee) they’ll retreat there when they feel threatened rather than try to jump.

  3. Unfortunately very healthy fish jump as much as or more than fish in questionable health. Heck, a healthy person can jump higher than a sick person. I lose fish by jumping and that is about the only way I lose them. Well, I don’t actually lose them, I find most of them eventually. But IMO the most likely cause for a fish to jump is that it is being chased by another fish or even a mate. If you have two males of many species, one will jump because they are always fighting. Fish in the sea jump all the time and if you have spent any time on a boat, you will see them. They are just not unfortunate enough to land on laminate flooring. Manta rays jump all the time which is why we don’t normally keep them in a nano.

    • "Caribbean Chris" Aldrich says

      If folks did try to keep manta rays in nanos, the Tang Police would have to form a new division…

      In the saltwater justice system, tank size offenses are considered especially heinous.
      In cities around the world, the dedicated detectives who investigate these vicious felonies are members of an elite squad known as the Special Manta Unit. These are their stories.
      DUN DUN

Speak Your Mind