Diamond Tetra
Moenkhausia pittieri
Also known as: Pittier's tetra
Diamond tetras are one of those fish that look kind of plain in the bag, then you get them settled in and they start throwing off this glittery, diamond-like shine when the light hits them-super satisfying to watch. They're active, always cruising around the midwater, and in a nice little school they'll do that tight, synchronized swimming thing that makes the tank feel alive.
Diamond Tetras possess a shimmering silver body adorned with distinct iridescent blue and red markings, particularly prominent on their fins.
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Quick Facts
Size
2.5 inches
Temperament
Peaceful
Difficulty
Beginner
Min Tank Size
20 gallons
Lifespan
3-5 years
Origin
South America (Venezuela - Lake Valencia basin)
Diet
Omnivore - quality flakes/micro pellets, plus frozen/live foods like brine shrimp, daphnia, and bloodworms
Water Parameters
24-28°C
5.5-7.5
5-12 dGH
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Calculate heater sizeCare Notes
- Keep them in a proper group (at least 6-8; 8-10 is even better). In small numbers they can become shy and may show more fin-nipping.
- A 20-gallon long works great for a school-give them open swimming space plus plants/wood around the edges so they feel secure.
- They do best in stable, clean water: about 75-82°F (24-28°C), pH ~5.5-7.5 (often best below neutral), ammonia/nitrite at 0, and nitrates kept low (commonly under ~20 ppm).
- Feed small amounts 1-2x a day: a decent flake/micro pellet as the staple, then rotate in frozen foods (daphnia, brine shrimp, bloodworms) to bring out color and keep them active.
- Good tankmates are other chill community fish (corydoras, small rasboras, peaceful dwarf cichlids); skip slow long-finned fish like bettas, fancy guppies, and long-fin angels unless you like chasing fin-nip drama.
- They color up more on a darker substrate with slightly dim lighting and some floating plants-bright, bare tanks tend to wash them out.
- Watch for stressy stuff: if they're hiding, clamping fins, or getting nippy, it's usually not enough schooling numbers, too small a tank, or water getting dirty between water changes.
- Breeding is doable if you're curious: condition them on live/frozen food, then move a pair/group to a separate tank with a spawning mop or fine plants-pull the adults after they scatter eggs because they'll snack on them.
Compatibility
Good Tankmates
- Other chill, mid-water schoolers like rummynose tetras or lemon tetras - they match the Diamond Tetra vibe and nobody gets weird about territory (just keep both in decent groups).
- Corydoras catfish - classic combo. Corys do their own thing on the bottom and Diamonds cruise the middle, so they don't bug each other at all.
- Small, peaceful plecos like bristlenose (Ancistrus) - good algae help and they're sturdy enough to ignore tetra drama, plus they mostly come out when the lights are low.
- Dwarf cichlids that aren't jerks, like a calm pair of apistos or a single German blue ram - works best in a planted tank with hides so nobody feels crowded.
- Peaceful gouramis like honey gourami - they're mellow and usually don't get the tetras all riled up (just avoid pairing one timid gourami with a too-small tetra group).
- Platies or mollies - can work, but only if you keep water parameters in a middle ground; avoid pairing them if you're maintaining very soft/acidic water for the tetras' optimal coloration and condition.
Avoid
- Fin-nippy troublemakers like tiger barbs or serpae tetras - Diamonds can get a little spicy themselves, and together it turns into nonstop chasing and shredded fins.
- Slow, fancy-finned fish like bettas or long-fin guppies - Diamonds are usually peaceful, but they will test those flowing fins, especially if the tetra group is small.
- Big aggressive stuff like convicts, green terrors, or most larger cichlids - they'll bully the Diamonds or straight-up snack on them once they size up.
1) Where they come from
Diamond tetras are from Venezuela, mostly around the Lake Valencia basin. They come from warm, often slightly tannin-stained waters with plants and leaf litter. That background explains a lot: they look their best under softer lighting, and they appreciate some cover instead of a bare glass box.
2) Setting up their tank
These are beginner-friendly fish, but they reward you if you give them a calm, planted setup. In a bright, empty tank they can look washed out and act a little jumpy. Give them a little “riverbank” vibe and they settle right in.
- Tank size: 20 gallons long is a sweet spot for a group; bigger is even better
- Group size: aim for 8–12 if you can (they really change in confidence when you keep a proper school)
- Filtration: any decent filter is fine; they like clean water and gentle-to-moderate flow
- Decor: plants (live or good fake), some wood or rock, and a darker substrate if you want their sparkle to pop
- Lighting: medium to low looks best; floating plants help a lot
- Lid: yes—these guys can jump when spooked
If your diamonds look “meh,” try dimming the light and adding floaters first. I’ve watched them go from silvery to properly glittery in a week just from calmer lighting and more cover.
Water-wise, they’re not divas. Neutral-ish water is fine, and they handle a reasonable range as long as it’s stable. I’ve had the best results keeping them warm (mid-70s °F) with regular water changes—clean water makes their fins and scales look sharper.
3) What to feed them
Diamond tetras eat like typical tetras: they’ll take flakes and pellets happily, but they really show better color and fuller bodies with a little variety. They’re quick at feeding time and usually not picky.
- Daily staple: quality flake or small micro-pellets
- Color/condition boosters: frozen bloodworms, brine shrimp, daphnia (a couple times per week)
- If you like live foods: baby brine shrimp and small worms get them fired up
- Feeding rhythm: small portions 1–2 times a day—enough that it’s gone in a minute or two
They’ll absolutely overeat if you let them. If you see slightly pinched bellies on some fish and big bellies on others, you’re either underfeeding or the bolder ones are hogging—spread food across the surface so everyone gets a shot.
4) How they behave and who they get along with
In a good-sized group, diamonds are peaceful and kind of “busy” in that fun tetra way—cruising midwater, flashing, and doing little pecking-order dances. Males can posture at each other, especially when they color up, but it’s usually all show.
- Best tankmates: other peaceful community fish (corys, small plecos, kuhli loaches, rasboras, peaceful barbs, most dwarf cichlids that aren’t aggressive)
- Also great with: calm gouramis and angelfish *if* your diamonds are full-grown and the angel isn’t a tetra-eater
- Use caution with: long-finned fish (occasionally a diamond will get nippy if the group is too small or the tank is tight)
- Avoid: fin-nipping magnets (slow, very long-finned fish in small tanks) and big predators that see tetras as snacks
Most “diamond tetra aggression” stories I’ve seen come down to two things: too few of them, or not enough swimming room. Add more diamonds and give them length (a 20 long beats a tall 20 every time).
5) Breeding tips (if you want to try it)
Breeding them is doable at home, but it’s not as automatic as livebearers. The main trick is protecting the eggs—adults will snack on them like it’s their job.
- Set up a small breeding tank (10–15 gallons works) with a sponge filter and gentle aeration
- Use a spawning mop, java moss, or a mesh/egg-crate bottom so eggs fall where adults can’t reach them
- Condition the pair/group for a week with frozen/live foods
- Spawning often happens at first light—dim room, then morning light tends to trigger it
- Remove adults right after you see spawning activity (or after a day if you’re not sure)
- Fry foods: infusoria/microworms at first, then baby brine shrimp once they’re big enough
I’ve had the best luck spawning tetras by using a small group (like 2 males, 3–4 females) instead of a single pair. More natural behavior, more eggs, and less “one fish gets stressed out” drama.
6) Common problems to watch for
Diamond tetras are hardy, but they still react fast to the usual community-tank issues. Most problems show up as faded color, clamped fins, hiding, or flashing (rubbing on decor).
- Ich after new fish: quarantine new arrivals if you can, and don’t add fish from a stressed-out store tank
- Fin nipping: usually from too small a group or a cramped tank—bump the school size and add plants/line-of-sight breaks
- Washed-out color: bright lighting, no cover, or poor diet (they look best with floaters + varied foods)
- Sudden losses: commonly ammonia/nitrite spikes or big swings in temperature—check your parameters before you start throwing meds at the tank
- Skinny fish in a group: food competition—feed in two spots or use sinking foods so shy fish get their share
If you see them gasping at the surface, don’t guess—test the water right away. Diamonds usually hang midwater; surface-gulping is often a water-quality or oxygen issue.
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