Discus Water Parameters (Temp + pH)
Short answer: Discus keepers run 84 F and pH 7.0. From 99 real discus tanks: median temp 84 F (IQR 83-86) and median pH 7.0 (IQR 6.5-7.6). Warmer and softer than a typical community tank.
Discus at a glance
- Scientific name
- Symphysodon aequifasciatus
- Adult size
- ~5.5″
- Temperature
- 82–86°F
- pH
- 5–7.5
- Minimum tank
- 55 gal
- Temperament
- semi aggressive
- Social
- schooling — keep 5+
- Reference
- Wikipedia
Discus keepers run their tanks at 84 F and a pH of 7.0. Those are the medians from the 99 real discus tanks in the AquaGauge dataset (July 2026 snapshot), compiled from r/discus posts where keepers shared actual water test results. That is 6 degrees warmer and 0.4 pH points more acidic than a typical community tank, which is why discus need their own parameter playbook.
What real discus keepers actually measure
| Parameter | N (tanks) | Median | Mean | IQR (Q1-Q3) | Full range |
|---|---|---|---|---|---|
| Temperature (F) | 27 | 84 | 84.1 | 83-86 | 75-88 |
| pH | 43 | 7.0 | 7.0 | 6.5-7.6 | 6.0-8.0 |
| Nitrate (ppm) | 68 | 10 | 17.9 | 2-18.75 | 0-400 |
| Ammonia (ppm) | 41 | 0 | 3.2 | 0-0 | 0-100 |
Two things stand out. First, discus tanks run hot: the middle half of keepers hold between 83 and 86 F. Second, pH is lower than the freshwater average (7.4 across all species in our dataset). The 7.0 median reflects captive-bred discus thriving in neutral water rather than the acidic blackwater of their wild range.
Temperature: 82-86 F
Discus (Symphysodon aequifasciatus) come from slow-moving Amazonian tributaries where water temperatures sit between 26 and 30 C (79-86 F).1 Real keepers cluster at the warm end of that range: the median is 84 F, and Q3 is 86 F. The coolest tank in the dataset sits at 75 F, well below the rest of the pack.
This warmth has consequences. Water at 84 F holds less dissolved oxygen than a 76 F community tank. That means discus tanks need stronger surface agitation or a canister filter with a spray bar to keep oxygen levels up. A 55-75 gallon tank gives enough water volume to buffer temperature swings.
Use a 200-300 W adjustable heater for a 55-75 gallon discus tank. Set it to 84 F and verify with a separate thermometer. Budget heaters drift, and a 2-degree drop overnight stresses discus more than most community fish.
pH: neutral works for captive-bred discus
The median pH is 7.0 with an IQR of 6.5-7.6. FishBase lists a tolerance range of pH 5.0-8.0 for the species, so the entire interquartile range from real keepers falls well within safe limits.1
Wild discus from the Rio Negro live in extremely soft, acidic blackwater (pH 4.5-6.0). But the discus sold in shops are almost all captive-bred through many generations. These fish have adapted to harder, more neutral water. Only 14% of keepers in our data run pH under 6.5.
If your tap water sits between 6.5 and 7.6, leave it alone. Chasing a low pH with chemicals or RO water creates instability, and a pH swing of 0.3 units in a few hours stresses discus more than a steady 7.2 does. The full freshwater pH breakdown covers adjustment strategies for keepers whose tap water falls outside this range.
Nitrogen: discus are sensitive
Discus are less tolerant of dissolved waste than hardier cichlids.
Nitrate: The median is 10 ppm and 85% of discus keepers stay at or below 20 ppm. Only 6% exceed 40 ppm. Many experienced discus keepers target under 10 ppm through 2-3 water changes per week.
Ammonia: The median is 0 ppm. Any detectable ammonia is an emergency in a discus tank. At pH 7.0 and 84 F, a larger fraction of total ammonia nitrogen exists as toxic free ammonia (NH3) than at lower temperatures. See safe ammonia levels for the full breakdown.
Seriously Fish describes discus as “very shy, skittish fish” that need substantial cover to feel secure.2 Stress from poor water quality or exposed layouts compounds that temperament, leading to darkened colors, clamped fins, and refusal to eat.
Discus vs. community tank parameters
Here is where discus parameters differ from a standard tropical community:
| Parameter | Discus median | Community median | Difference |
|---|---|---|---|
| Temperature | 84 F | 78 F | +6 F |
| pH | 7.0 | 7.4 | -0.4 |
| Nitrate target | under 10 ppm | under 20 ppm | Stricter |
The temperature gap is the biggest constraint on tankmates. Most community fish prefer 74-78 F and stress at 84 F. Compatible species include cardinal tetras, rummy-nose tetras, ram cichlids, and some corydoras species that tolerate warmer water. Use the stocking calculator to model your exact combination.
How we counted
AquaGauge compiled 99 discus setups from public Reddit posts (r/discus) where keepers shared water test results. That gave us 27 temperature readings, 43 pH readings, 68 nitrate readings, and 41 ammonia readings. Each parameter has its own sample size because not every post reports every number. Full methodology at /methodology/. 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 Discus tank. We start with your discus 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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Fluval M 200W Submersible Heater Holds a steady 84 F in a 55-75 gallon discus tank without the drift common in budget heaters. Check price on Amazon → -
PAIZOO Digital Aquarium Thermometer Accurate to 0.9 F so you can verify your heater holds the 82-86 F target discus need. Check price on Amazon → -
API Freshwater Master Test Kit Liquid tests for ammonia, nitrite, nitrate, and pH cover every parameter discus are sensitive to. Check price on Amazon →
FAQ
- What temperature do discus need?
- 82-86 F. Across 27 real discus tanks, the median is 84 F and the middle half fall between 83 and 86 F. Discus run about 6 degrees warmer than a typical community tank.
- What pH do discus need?
- Most discus do fine between 6.5 and 7.6. Across 43 tanks, the median pH is 7.0 and 56% of readings fall between 7.0 and 8.0. Wild discus prefer softer, more acidic water, but captive-bred stock adapts to neutral.
- Do discus need soft water?
- Wild discus live in very soft, acidic blackwater (pH 5-6). Captive-bred discus, which are the vast majority in the hobby, adapt to neutral pH (median 7.0 in our data) and moderate hardness. Stability matters more than chasing a low number.
- How much nitrate is safe for discus?
- Keep nitrate at or below 20 ppm. 85% of discus keepers in our data do exactly that, with a median of 10 ppm. Discus are sensitive to dissolved waste, so frequent water changes are standard practice.
Sources
- Symphysodon aequifasciatus summary, FishBase. View source ↗
- Symphysodon aequifasciatus, Seriously Fish. View source ↗
Freshwater aquarist of 8+ years.