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Keeping Monos and Scats

Monos and scats are interesting aquarium fish to keep.

By Jeremy Gosnell |

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Scat fish - Scatophagus argus
Scat (Scatophagus argus)
By Tony Terceira.
Mono fish - Monodactylus sebae
Mono (Monodactylus sebae)
By Tony Terceira.
Q. Is it possible to mix brackish water fish like monos and scats with freshwater fish species. I would like to try this but I would like to know if it will it work?
Mary Ann Matthews
Indiana

A. When you consider that both the mono (Monodactylus sebae) and scat (Scatophagus argus) are brackish water fish that can easily be acclimated to the saltwater environment, it becomes hard to think that they could comfortably live in fresh water. While brackish water fish vary in their tolerance to higher or lower salinities, both these fish are rather hardy when considering the environment change. A couple of interesting things come up when we look at many brackish water species. At one point in their lives they will often tolerate fresh water, though as they mature they must be slowly moved into the saltwater environment. For both the mono and the scat it is possible to keep young fish in fresh water. The mistake that many aquarists make is that they acclimate the fish to fresh water and then leave it there long term without researching the fish’s need to move to a more saltwater environment as it grows.

It may be possible to mix the mono and scat with freshwater fish temporarily but not long-term, though I can’t really recommend it. Both the mono and scat require a large aquarium. They are both active fish so open swimming room is important. The maximum size for a mono is around 8 inches with a scat eventually growing to a similar size. A 55-gallon fish aquarium may be suitable for either fish species, though a larger aquarium is always better. It would be rather painstaking (due to fish size and aquarium requirements) to have to move the fish from one aquarium to another. Better success would be accomplished with having a species aquarium that would house the fish from the start.

Typically, the aquarist would slowly increase the salinity of the water as the fish grow. The eventual goal would be an aquarium made up of sea water density around 1.023. At this point hermit crabs, snails and other saltwater invertebrates could be added to the aquarium. Even compatible saltwater fish would be an option. I believe the excitement of watching a fish transition through various life stages (freshwater to saltwater) is what draws people to keeping animals like monos and scats.

In my experience monos have proved far hardier than scats. I found that scats are prone to ich. It is interesting to note that monos spawn in the high-salinity waters of the ocean. One thing to be aware of is that in the wild, monos consume a large amount of algae and aquatic plant matter. It is important that this diet be replicated in the home aquarium as it would contribute greatly to the health of the fish.

Overall, monos and scats are exciting fish that are very different from any other saltwater or freshwater animal. The unique stages they take when going from juvenile to adult make them highly interesting and I would assume for the prudent aquarist very rewarding. To have a saltwater aquarium that is stocked with fish that you worked through several demanding life stages would be rewarding and no doubt serve as a highly interesting conversation piece.

One thing that keeps many aquarists from keeping either species is both their large size and the demands they present as they grow older. However, I think that any aquarist could learn a lot about these interesting animals and aquatic ecosystems in general by transitioning these fish through their freshwater juvenile stage up to their adult saltwater stage.

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Keeping Monos and Scats

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Reader Comments

Dot    Hawk Junction, ON

3/26/2012 5:01:21 AM

Great article. Both nice fish to keep.

Vixen    Alta, CA

9/16/2010 12:34:00 PM

Both very interesting looking fish. Thanks for the info! :)

Brian    Louisville, KY

2/16/2009 5:07:30 AM

Thanks for sharing this information. I had not thought about this before.

Noman    alexandria, YT

11/25/2008 7:32:55 AM

with full respect for the writer, but I have Monos in totally fresh water since 2 years!

I start with 10 monos, their size was around 1 inch, I kept them in very large Aquarium (about 120 Gallon) along with 1 small sliver arwana, and 3 stying rays and some mixed nife fishes.

after 2 years, I have only 7 monos, more than 8 inches each .. further more, they are spawning almost every 10-15 days, they spawn all togeather releasing 1000s of very tiny crystal clear eggs (I never be able raise the fry.. but this is long story!) making great meal to all aquarium fishes :)

again, they never been in brakish water.

(I'm from Egypt, there is no country field in the comment form)

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