Corydoras Water Parameters (Temp + pH)
Short answer: Corydoras keepers run 78 F and pH 7.5. Across 676 real cory tanks, the median temp is 78 F (IQR 76-80), the median pH is 7.5 (IQR 7.0-7.8), and 87% keep nitrate at or below 20 ppm. Here is the full breakdown.
Corydoras catfish at a glance
- Scientific name
- Corydoras sp.
- Adult size
- ~2.5″
- Temperature
- 72–80°F
- pH
- 6–7.5
- Minimum tank
- 20 gal
- Temperament
- peaceful
- Social
- schooling — keep 6+
- Reference
- Wikipedia
Corydoras keepers run their tanks at 78 F and a pH of 7.5. Those are the medians across 676 real cory keeper tanks in the AquaGauge dataset (July 2026 snapshot), compiled from r/corydoras posts where keepers shared actual water test results. The numbers land tighter than most care guides suggest, and well within the 72-82 F, pH 6.0-8.0 tolerances that FishBase lists for the species.1
Corydoras water parameters at a glance
| Parameter | ScotCat (recommended) | Real tanks (AquaGauge) |
|---|---|---|
| Temperature | 20–27 °C (67–81 °F)4 | median 78 °F (37 tanks) |
| pH | 6.5–7.24 | median 7.5 (76 tanks) |
ScotCat's recommended ranges for the bronze cory beside our real-tank medians (from our corydoras dataset). Real pH sits a touch above the recommended ceiling, but well within the species' wider tolerance.
What real corydoras keepers actually measure
| Parameter | N (tanks) | Median | Mean | IQR (Q1-Q3) | Full range |
|---|---|---|---|---|---|
| Temperature (F) | 37 | 78 | 77.7 | 75.5-80 | 72-86 |
| pH | 76 | 7.5 | 7.4 | 7.0-7.8 | 6.0-8.4 |
| Nitrate (ppm) | 119 | 10 | 15.9 | 5-20 | 0-160 |
| Ammonia (ppm) | 103 | 0 | 1.9 | 0-0 | 0-40 |
| Nitrite (ppm) | 103 | 0 | 4.6 | 0-5 | 0-50 |
Two things stand out. First, the temperature cluster is tight: the middle half of tanks sit between 75.5 and 80 F, right in the tropical community range. Second, ammonia is overwhelmingly zero: median, Q1, and Q3 are all 0 ppm. Any detectable ammonia is an emergency, not a normal reading.
Temperature: 76-80 F
Corydoras are tropical South American catfish. The median temp across 37 tanks is 78 F. Nobody in the data runs below 72 F, and only outliers exceed 82 F. This aligns with Seriously Fish’s recommended range of 72-79 F for Corydoras aeneus.2
A 50 W adjustable heater holds this range in a 20-gallon tank, which is the median tank size for cory keepers in our data (n=493). Set it to 78 F and verify with a separate thermometer. Below 72 F, metabolism and immune function slow. Above 82 F, dissolved oxygen drops and stress increases.
pH: stability over precision
The median pH is 7.5 with 79% of readings between 7.0 and 8.0. Only 5% of cory keepers report pH under 6.5. If your tap water lands between 7.0 and 7.8, leave it alone.
Wild-caught corydoras from blackwater tributaries prefer softer, more acidic water. But captive-bred stock (the vast majority of what shops sell) adapts to a wide range. Chasing a lower pH with chemicals creates the parameter swings that stress bottom-dwellers more than a steady 7.5 does. See the full freshwater pH breakdown for cross-species context.
Nitrogen: the bottom-dweller tax
Corydoras live on the substrate, right where waste settles. That makes nitrogen levels matter more for them than for mid-water fish. For a full picture of corydoras care including groups, substrate, and tankmates, see the hub page.
Nitrate: The median is 10 ppm and 87% of cory keepers stay at or below 20 ppm. Only 6% exceed 40 ppm. Keep nitrate under 20 ppm with regular water changes and avoid overfeeding.
Ammonia and nitrite: Both should read zero in a cycled tank. The median for both is 0 ppm. The non-zero readings in the data (ammonia mean 1.9, nitrite mean 4.6) come from keepers posting during cycling crashes or emergencies. If you see any ammonia or nitrite, act immediately: safe ammonia levels breaks down the thresholds.
William T. Innes described corydoras long ago as “a quaint little fish and very well adapted to life in the aquarium. Principally a ground-feeder, it is regarded as something of an aquarium scavenger.”3 That ground-feeding habit is exactly why clean substrate and low nitrogen matter for this species.
How we counted
AquaGauge compiled 676 posts from r/corydoras where keepers shared water test results, tank photos with visible readings, or parameter logs. Each field (temp, pH, ammonia, nitrate, nitrite) has its own sample size because not every post reports every parameter. All statistics are computed from the raw readings with no filtering or outlier removal. See our full methodology for details. Figures are from the July 2026 snapshot (6,414 tanks total).
Check your exact stocking
Add your fish below to see stocking %, filtration load and compatibility for your setup — live.
Planning a Corydoras catfish tank. We start with your corydoras catfish and filter the list to compatible tankmates — untick to see every species (incompatible ones get flagged).
Stocking — under 85% comfortable · 85–100% full · over 100% overstocked
Show the math
Gear for this setup
As an Amazon Associate AquaGauge earns from qualifying purchases. Some links below are affiliate links, at no extra cost to you. Current price and availability are shown on Amazon. Disclosure.
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AQUANEAT Aquarium Heater (50 W) Adjustable submersible heater with thermometer, sized right for a 20-gallon corydoras tank. Check price on Amazon → -
API Freshwater Master Test Kit (800 tests) Liquid reagent kit covers pH, ammonia, nitrite, and nitrate so you track real numbers instead of guessing. Check price on Amazon → -
Aqua Natural Sugar White Sand (10 lb) Smooth, barbel-safe sand that lets corydoras sift naturally without abrasion. Check price on Amazon →
FAQ
- What temperature do corydoras need?
- 76-80 F. Across 37 real cory tanks, the median is 78 F and the middle half fall between 75.5 and 80 F. A stable temp in that range matters more than hitting an exact degree.
- What pH do corydoras need?
- Most corydoras do fine between 7.2 and 7.8. Across 76 tanks, the median pH is 7.5 and 79% of readings fall between 7.0 and 8.0. Stability beats precision.
- How much nitrate is safe for corydoras?
- Keep nitrate at or below 20 ppm. 87% of cory keepers in our data do exactly that, with a median of 10 ppm. Nitrate above 40 ppm stresses bottom-dwellers that sit in the waste layer.
- Do corydoras need soft water?
- Not necessarily. Most keepers run neutral to slightly alkaline water (pH 7.0-7.8) with no special buffering. Wild-caught corydoras prefer softer water, but captive-bred stock adapts to a wide range.
Sources
- Corydoras aeneus (Bronze Corydoras), FishBase. View source ↗
- Corydoras aeneus, Seriously Fish. View source ↗
- The Complete Aquarium Book.
- ScotCat catfish factsheets, ScotCat (electronic publication) (2025). View source ↗
Freshwater aquarist of 8+ years.
