I was recently given a 3″ long Monodactylus argenteus. (Thanks to TL)
This Mono had been kept in brackish water that was about half the salinity of seawater. When Monos are young they are generally kept in a brackish tank. My only option was to put him in my saltwater tank.
I took 2 days to transfer him to full saltwater.
I’ll just briefly run down the positives and negatives of owning a Mono.
The positives:
He is the most lively fish in the tank. He eats any kind of fish food. He is not aggressive at all. He (or she) looks great!
My friend who owned this fish named him Stereo! (Clever, eh?)
The negative:
Just one problem, the Mono gets huge. My tank is 42 gallons and I would never get a Mono and expect to keep him forever. As this Mono gets larger I should be able to give him to someone with at least a 75 gallon tank. In the wild, the Mono gets as big as a dinner plate.
The other issue is that the wild Mono is a schooling fish. To keep a school of Monos would take a huge tank. I wish I could keep some friends for this fish but it just isn’t possible. On the plus side, he certainly isn’t sulking from loneliness.
It takes about 10 pictures of a Mono to get one that’s not blurry.
If you have a big saltwater tank I completely recommend the Mondactylus argenteus.
A Practical Fishkeeping Blog 
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