Silver Moony
Monodactylus argenteus
Monodactylidae
About
A disc-shaped, mirror-silver shoaler from the mangrove estuaries, tidal creeks and lower river reaches of the Indo-West Pacific, ranging from the Red Sea and East Africa to Samoa, New Caledonia and northern Australia. Juveniles carry two dark bars, one through the eye and one just behind the gill cover, while the tall yellow-edged dorsal and anal fins stretch the body into an almost perfect diamond. Adults reach roughly 25 cm and cruise the open mid-water in tight, fast-moving groups, flashing like coins under the lights. They are nervous fish: a sudden movement outside the glass sends the whole shoal bolting, and in a small or bare tank that panic ends in bruised snouts and broken scales.
Care
Brackish for life, not just for a phase. Start juveniles at about SG 1.005-1.010 and raise the salinity over months as they grow, toward SG 1.018-1.022 or near-marine for adults; keeping monos permanently in freshwater is the classic way these fish are killed, exactly as with green spotted puffers. Use a proper marine salt mix, not tonic salt. Give a group of at least five a tall, long tank of 150 cm or more with hard alkaline water, powerful filtration, strong oxygenation, open swimming lanes and a few shaded retreats. A tight-fitting lid is mandatory: they are excellent jumpers and they spook easily.
Diet
Feed spirulina or algae pellets and flakes as the staple, and rotate frozen or live mysis, brine shrimp, krill and chopped prawn in several times a week. Offer blanched spinach, peas or nori regularly; a diet of dried protein alone leads to poor condition. Two modest feeds a day keep water quality manageable in a heavily stocked brackish system.
Tankmate compatibility
Possible with care (12)
Avoid (259)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
There is no reliable way to sex this species by eye. That is the honest answer, not a gap in our data.
All the methods, with diagramsAlso in these lists
Frequently asked questions
- What tank size does a Silver Moony need?
- A Silver Moony needs an aquarium of at least 450 litres (118.9 US gallons) with a footprint at least 150 cm (59.1 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Silver Moony need?
- Silver Moony does best at 24–28 °C (75.2–82.4 °F), pH 7–8.5 and a general hardness of 10–30 °dGH.
- What group size does a Silver Moony need?
- Silver Moony is a social species — keep a group of at least 5 so natural behaviour emerges and stress stays low.
- Is the Silver Moony suitable for beginners?
- Silver Moony is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.