Can Cardinal Tetra live with Oscar?
Not recommended
Why
- Oscar’s mouth is big enough to swallow Cardinal Tetra (only 2" long) — it will be eaten.
- Oscar is aggressive and will attack the peaceful Cardinal Tetra.
- Only a narrow water hardness overlap — keep both around 5–6 dGH.
Side-by-side
| Cardinal Tetra | Oscar | |
|---|---|---|
| Temperature | 73–81°F | 74–81°F |
| pH | 5–7 | 6–8 |
| Hardness (GH) | 1–6 dGH | 5–20 dGH |
| Adult size | 2" | 16" |
| Temperament | Peaceful | Aggressive |
| Min tank | 15 gal | 75 gal |
Together, plan on at least 75 gallons.
Compatible alternatives
Instead of Cardinal Tetra (to keep Oscar):
- Oscar — 16", aggressive buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
- Giant Gourami — 24", semi-aggressive buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
- Typhoon Pleco — 12", semi-aggressive buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
Instead of Oscar (to keep Cardinal Tetra):
- Sparkling Gourami — 1.5", peaceful buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
- Pygmy Cory — 1", peaceful buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
- Sailfin Molly — 5", peaceful buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
Where to buy
- Cardinal Tetra: buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
- Oscar: buy at Flip Aquatics · Flip Aquatics live-arrival guarantee
Live-animal shipping: add a heat pack below 50°F, expect weather holds above 90°F, and schedule delivery for a moderate week when someone can receive it promptly.
Build a full tank around this stocking →Everything compatible with Cardinal Tetra · …with Oscar