Can Cardinal Tetra Live With Guppy?
Sometimes, this pairing works in a neutral-pH community tank, though cardinal tetras prefer softer, more acidic conditions.
Why
- Cardinal tetras need soft, acidic blackwater (pH 5.0-7.0 ideal, tolerating up to 7.0 in harder water).
- Guppies prefer hard, alkaline water (pH 7.0-8.0) and do not thrive in acidic conditions.
- The temp overlap (73-81F) is wide, but the pH overlap is only a single point at 7.0.
- Both species are peaceful and similar in size (cardinals 2 inches, guppies 2 inches).
- Fishkeepers have mixed results , success depends on maintaining pH right at the edge of both tolerances.
What could go wrong
Cardinal tetras kept at pH 7.0 long-term lose color intensity and may develop ragged fins, while guppies in soft acidic water become more prone to disease.
Gear for a shared tank
Sized for the 15 gallon minimum this pairing needs. Affiliate links — we earn a small commission if you buy through them.
AquaClear 30 Power Filter
Oversized filtration is what lets you stock two species together without water quality crashing. Rated for a tank slightly larger than the 15 gallon minimum.
Eheim Jager 150W Thermostat Heater
Holds a steady temperature inside the 73-81°F window both species need.
API Freshwater Master Test Kit
Keep ammonia, nitrite, and nitrate in check. Two-species tanks have more bioload and less margin for error than single-species setups.
Better pairings to consider
This works if you target pH 6.8-7.2 with buffering substrate or driftwood. If you cannot hold pH in that range, keep cardinals with other soft-water tetras or keep guppies with hard-water livebearers.
Related compatibility questions
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