Before you buy discus: the complete 7-step checklist

In short

• Never buy discus before the aquarium is fully cycled — cycling takes 4–6 weeks.
• Buy at least 4–6 fish of similar size (5–8 cm / 2–3.1 in), never 1–2 on their own.
• Check 7 visual signs of health before you pay (colors, eyes, fins, droppings).
• Choose a verified source: a trusted local breeder, a specialist aquarium store, or a reputable importer (e.g. Stendker through an authorized distributor).
• Ask for the seller's water parameters (pH, TDS, temperature) so you can plan a gradual transition.
• Prepare drip acclimation before transport (1–2 hours) — it markedly reduces post-transport mortality.

💱 This guide focuses on the process and checks of buying discus, which apply everywhere. Discus, gear and livestock prices vary enormously by country, so we don't publish fixed international prices. Where Romania-specific figures appear, they are clearly labelled as a Romania estimate — replace them with your own local prices.

What you'll learn

Buying discus (Symphysodon) is the most critical — and most underestimated — moment in the hobby. A large share of beginner failures happen in the first two weeks after purchase, and the usual causes are an unprepared tank, the wrong source, or sick fish bought without proper checks. This guide gives you a 7-step checklist, practical criteria for evaluating sources, the 7 visual signs of health to verify in person, and how to think about a realistic budget.

The 7-step checklist — before you hand over any money

1. A prepared, cycled aquarium — rule #1

Never buy discus before the aquarium is fully biologically cycled. An uncycled tank accumulates ammonia and nitrite within 24–72 hours and can wipe out the whole group.

How to confirm it's cycled:

• ✅ Ammonia: 0 ppm (e.g. API test)
• ✅ Nitrite: 0 ppm
• ✅ Nitrate: 5–20 ppm (a sign the cycle is working)
• ✅ A stable pH for 2 consecutive weeks

Cycling takes 4–6 weeks unaided, 1–2 weeks with starter bacteria (e.g. Seachem Stability, Tetra SafeStart, Prodibio BioDigest), or 3–7 days with mature filter media from an established aquarium.

See the full guide Cycling a discus aquarium step by step.

2. Trustworthy sources — how to compare

Verified local breeders ⭐ (recommendation #1)

Why they're usually the best option:

• You can see the real growing conditions (an on-site visit)
• You learn the water parameters and the fish's history
• An easier transition — often the same local water source
• A short transport time
• Proof of origin

How to find them depends on your country — look for breeder directories, club listings and recommendations from experienced keepers. In Romania, see verified discus.ro breeders.

Specialist aquarium stores

Acceptable if:

• You visit the physical store first
• The discus are kept at 28–30°C (82–86°F) — not with other tropicals at 25°C (77°F)
• They're in dedicated tanks, without overcrowding
• Staff can tell you the water parameters

Reputable importers (e.g. Stendker via an authorized distributor)

For keepers who want a known European bloodline:

• Stendker Diskuszucht (Germany) has decades of breeding experience
• Their fish are raised in hard water (TDS 250+), which can ease the move to harder tap water
• Authorized distributors deliver periodically in many countries
• Expect a higher price than local juveniles

Generic online sellers — avoid

❌ Best avoided:

• Generic pet shops where discus are kept incorrectly (e.g. with other species at lower temperatures)
• Animal markets or classifieds with no checks
• Direct Asia imports for beginners — transport mortality can be very high
• Sellers without current photos/video of the exact fish

3. The 7 visual signs of health — check in person

Spend at least 15 minutes watching the tank before you pay.

💡 Ask the seller to feed the fish while you watch. A healthy discus comes straight to food. One that has refused food for 2–3 days running is a warning sign (possible hexamitiasis or parasites). See Discus body language.

4. How many discus to buy — the group rule

At least 4–6 fish, never 1–2. Discus are gregarious (they live in groups in the wild). Fewer than 4 leads to a lopsided, aggressive hierarchy, and the weakest fish often succumbs to chronic stress within a few weeks.

Golden rules:

• Keep all discus a similar size (no more than ~±2 cm / ±0.8 in apart) — otherwise larger fish intimidate smaller ones
• Buy them from the same source, on the same day — this avoids double quarantine and cross-infection
• Prefer juveniles 5–8 cm (2–3.1 in) — they adapt to your water more easily than adults

See Discus tank size for an exact liters-per-fish calculation.

5. Check the seller's water parameters

Always ask before buying (the source water data):

• pH
• TDS (Total Dissolved Solids, in ppm)
• Temperature
• KH/GH

Why it matters: if your tank water differs a lot (pH ±0.5, TDS ±100 ppm), the transition must be made gradually through small daily water changes — not abruptly on arrival. Large differences cause osmotic stress and raise mortality in the first 7 days.

Tip: Stendker recommends TDS 250–350, pH 7.0 (adapted to hard European water). Asian discus are often grown at TDS 100–150, pH 6.5, which can make the transition to harder tap water more difficult.

6. Correct transport — container and thermometer

Materials needed:

• Oxygenated aquarium bags (ask the breeder/store)
• An expanded-polystyrene box (thermal insulation)
• A digital thermometer
• A chemical hot pack in winter (or a dual hot/cold pack across seasons)
• Newspaper/paper to darken the bags

Transport rules:

• A maximum of about 6 hours in sealed, oxygenated bags
• Hold the temperature at 28–30°C (82–86°F) ±1°C the whole way
• Keep them in the dark (it sharply reduces stress)
• Don't open the bags en route

See the detailed guide Transporting discus — how to do it right.

7. Prepare the tank for drip acclimation

Before the discus arrive home:

• ✅ Tank temperature confirmed: 28–30°C (82–86°F)
• ✅ Parameters checked last: 0/0/<10
• ✅ Lights off or at 10–20% (reduces stress for the first 24h)
• ✅ The drip container ready (a clean plastic bucket + airline tubing)
• ✅ The tank free of aggressive tank mates (separate them temporarily if needed)

The drip procedure takes 1–2 hours and markedly lowers post-transport mortality. See Acclimating new discus — the drip method step by step.

Realistic budget per fish — what drives the price

We don't publish fixed international prices, because discus prices vary widely by country, variety, size and source. Instead, here's what makes one fish cost more than another, so you can read your local market:

Plan for a group of at least 6. Buying the whole group at once (same source, same day) costs more upfront but avoids the losses and conflict that come from adding fish later.

🧮 Work out your total startup cost (tank + equipment + fish) and a monthly estimate with the cost calculator.

🇷🇴 Romania estimate (for local readers)

For readers in Romania (2026): local juveniles run roughly 100–200 RON/fish, local select subadults 200–400 RON, Stendker juveniles 250–450 RON, premium varieties 450–800 RON, rare Asian varieties 350–700 RON, and wild-caught discus 800–2,000+ RON. A group of 6 therefore costs about 600–1,500 RON locally or 1,500–3,000 RON for Stendker. These are Romania-specific figures — treat them as a local example, not an international benchmark.

Common mistakes — what to avoid

❌ "They're on sale, dirt cheap" — suspiciously cheap discus usually come from dubious sources and are often sick or poorly raised.

❌ "I'll just take 2 now and buy more next month" — discus form hierarchies, and later additions almost always get bullied.

❌ "The tank is new but I added a filter, so it's fine" — without a tested biological cycle, ammonia can kill the fish within a couple of days.

❌ "I bought from 3 different sources for variety" — this risks cross-infections (e.g. hexamitiasis, parasites) that are very hard to treat at once.

❌ "The seller told me they're healthy" — verify the 7 visual signs yourself; never take the seller's word for it.

Final checklist — ready to buy?

Tick every point before you go to the breeder/store:

• ☐ Aquarium cycled and tested for 2 consecutive weeks (0/0/<10)
• ☐ Tank temperature stable at 28–30°C (82–86°F) with a digital thermometer
• ☐ Budget per fish confirmed (for a group of at least 6)
• ☐ Source identified (a verified breeder or specialist store)
• ☐ Seller's water data obtained (pH, TDS, temp)
• ☐ Transport materials ready (O₂ bags, polystyrene box, thermometer)
• ☐ Tank prepared for drip (bucket, tubing, lights off)
• ☐ You've read Acclimating new discus and Simple quarantine

If you ticked all 8, you're ready. If one is missing, postpone the purchase until it's done.

What to do next

📚 Learn more: How to choose a healthy discus — 7 visual signs — a guide with photos and examples.

🧮 Calculate: volume, stocking and monthly cost — check whether your tank supports the group you want.

🛒 Buy: Verified breeders — filter by location, variety and price.