Rummy-nose tetras are silver torpedoes with a glowing red face and a boldly striped tail, famous for schooling more tightly than almost any other aquarium fish.
A group moving as one is a genuine spectacle.
They carry a built-in diagnostic: the red nose drains to washed-out pink when the fish are stressed or the water deteriorates, making the school a live water-quality gauge.
Housing
Keep a school of ten or more in a mature, cycled aquarium of 75 litres (20 gallons) or larger — bigger groups in longer tanks school more impressively.
Provide open swimming length with planted flanks.
Hold the temperature at 24-28C.
They come from soft, acidic blackwater, and while tank-bred stock adapts to moderately hard water, what they cannot forgive is instability: drift and spikes show in the noses immediately.
Diet
Offer fine flake or micro-pellets as the staple, with regular frozen or live treats such as daphnia, cyclops, baby brine shrimp, and chopped bloodworm.
Their mouths are small, so size food accordingly.
Feed once or twice daily in small amounts.
A well-fed, settled school shows saturated red noses at every feed.
Health
Rummy-noses are not delicate once settled, but they ship poorly and resent new, unstable tanks; add them to mature aquariums only and quarantine first.
Losses in the first fortnight usually mean the tank, not the fish, was not ready.
After that, standard tetra care applies: watch for ich after temperature dips and keep nitrate low with steady weekly water changes.
Faded noses are the early-warning sign — investigate before anything else goes wrong.
Temperament
Completely peaceful, rummy-noses spend the day cruising in formation through the lower midwater.
The tighter the school, the more secure the fish — small groups huddle and hide instead.
They are ideal companions for other gentle blackwater species: cardinal tetras, corydoras, dwarf cichlids, and pencilfish.
Nothing about them threatens shrimp colonies beyond the odd newborn.
A good fit for
Keepers who want true, dramatic schooling behaviour
Mature planted aquariums with stable parameters
Communities with dwarf cichlids and corydoras
Aquarists who like visible feedback on water quality
Common mistakes to avoid
Adding them to brand-new, unstable tanks
Groups under 8-10 that huddle rather than school
Temperature and parameter swings — noses fade fast
Buying freshly imported, unrested stock
Is your enclosure big enough?
Minimum volume75 litres (20 US gallons)
CompanyCannot be kept alone. The minimum is 10, and the space above is for that group.
In a fish tank the patient is usually the water. Test before you treat — dosing a healthy tank for a disease it does not have makes things worse.
Go now
Any detectable ammonia or nitrite in a stocked tankLarge water change now with dechlorinated, temperature-matched water. Stop feeding. Test again in 12 hours. Both are directly toxic. How toxic the ammonia reading is depends on pH and temperature, so the same number can be harmless or lethal.
Now
Fish gasping at the surface, or crowding the filter outflowIncrease surface agitation immediately, then test the water. Either the oxygen has crashed or the gills are being chemically burned. Both are hours-scale problems.
Now
Sudden deaths, more than one fish in a dayTest ammonia, nitrite, nitrate and temperature before doing anything else. Do not add medication yet. Multiple simultaneous deaths point at the water or the equipment, not at a pathogen.
Now
Today
Flashing — repeatedly scraping against decor or substrateTest the water, then look closely for parasites. Irritation is either chemical or parasitic; the test tells you which before you medicate.
Today
White salt-grain spots over the body and finsBegin the appropriate treatment today and check the temperature. The parasite's life cycle is temperature-driven, and it multiplies with every cycle you wait.
Today
Soon
Clamped fins, hiding, or refusing food for more than two daysTest the water and review recent changes. Usually the earliest visible sign of a parameter drifting.
A few days
Never add a new fish to a tank that is not fully cycled, and never treat blind. A test kit is cheaper than the fish.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Intermediate
Intermediate
Beginner
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Intermediate
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