Mono (Moony) Care Guide

Mono (Moony) (Monodactylus argenteus and M. sebae) is an intermediate-level freshwater fish that needs at least 90 gallons and 75-82°F. A tall, silver, disc-shaped fish that is often sold as a juvenile in plain freshwater. Adults do much better in brackish water, and many keepers move them toward full marine strength over time. They are active schooling fish that need a large tank with open swimming space.

Care facts at a glance

Quick tips

• Plan to raise the salinity gradually; do not keep adults long term in plain freshwater.
• Use a salt mix made for aquariums and measure with a hydrometer or refractometer.
• Keep a group of three or more in a long tank; avoid small tankmates that fit in the mouth.

San Diego water

Naturally suited to San Diego's hard, alkaline tap water once it is dechlorinated (the city uses chloramine, so use a conditioner that handles it). Learn the numbers in our San Diego tap water guide.

Before you buy

Make sure your tank is cycled (how to cycle a tank), check your numbers with the water testing guide, and use the compatibility guide to check tankmates. These are general ranges; individual fish and local water vary.