Complete Beginner Guide

Not for a first aquarium. Discus require a high temperature (29–30°C), stable parameters and frequent water changes. Recommended after at least 6–12 months of experience with tropical fish.

As a Romania estimate (2026), roughly €30–60/month (150–300 RON) for 6 discus in 250L: electricity (~€12–20), food (~€8–16), dechlorinator + tests (~€4–8), water changes (free if you have tap water). Costs vary a lot by country — see our calculator for an estimate based on your own tariffs.

As a Romania estimate (2026), a complete setup for 6 discus runs roughly €500–1100 (2500–5500 RON): a 250L aquarium (~€200), an external filter (~€100–160), heaters (~€40), tests + accessories (~€60), plus 6 discus at ~€20–30 each (~€120–180). Prices vary widely by country and supplier.

An aquarium cycled for 4–6 weeks, stable parameters (ammonia + nitrite = 0), a temperature of 29–30°C, a working filter, dechlorinator, and a quarantine spot if you already have fish.

Minimum 200L for 5–6 discus. 250–300L recommended for a healthy group with room for hierarchy. Below 150L = chronic stress, high mortality.

An external filter with a flow rate of 4–6× the volume/h. For 250L → 1000–1500 L/h. Trusted brands: Eheim Classic 600, Fluval 307, JBL CristalProfi e1502. Avoid small internal filters.

Cycling = growing the beneficial bacteria that turn toxic ammonia into nitrite, then into less dangerous nitrate. It takes 4–6 weeks. Without it, discus die within 48–72h from poisoning.

Ask for filter sponges from a breeder with a mature aquarium — a ready-made bacterial colony, cycling in 3–7 days. Or use Seachem Stability/Tetra SafeStart according to the instructions.

For beginners: bare-bottom (no substrate) is easier to clean and lets you spot health problems. Fine sand substrate (0.5–1mm, max 3cm layer) is fine for aesthetics, but needs weekly vacuuming. Avoid gravel — it traps waste.

The rule is 1W/liter (1.2W/L in winter). For 200L → 200W total, ideally 2 heaters of 100W (safety against failures). Trusted brands: Eheim Jäger, Aquael Comfort Zone, JBL ProTemp, Fluval E. Add an external Inkbird thermostat for ±0.2°C precision.

Power of 0.3–0.5 W/L for a moderately planted tank, 6500K full spectrum, 8–10 hours/day with a mandatory timer. RO 2026 models: Chihiros A2 Plus (350–550 RON), Aquael Leddy Slim Plant (250–450 RON), Twinstar S-Line premium (800–1200 RON). Discus prefer diffuse light.

Top 4 'set-and-forget' plants: Anubias (any variety, on driftwood), Microsorum pteropus (Java Fern), Cryptocoryne wendtii, Ceratophyllum demersum (floating). All tolerate 30°C, need no CO2, low light. Avoid Glossostigma, HC Cuba, Cabomba — they die above 26°C.

Below 300L → external filter (Eheim, Fluval, JBL, 300–1500 RON, plug & play). Above 400L → a sump becomes feasible (1500–5000 RON, more filter volume, hides equipment). Beginners and locations sensitive to flooding: the external filter is always the safe choice.

1 Terminalia catappa leaf per 30L of water (200L → 6–8 leaves). Add gradually, 2–3/week, to avoid a sudden pH drop. Benefits: antibacterial tannins, natural pH 6.0–6.5, reduced stress, encourages breeding. Replace every 3–4 weeks.

7 signs: clear eyes with no cloudiness, vivid colors without paleness, fully spread fins, a round (not thin) body, calm breathing, eats actively when fed, doesn't rub against the décor.

Minimum 5–6 fish of the same size, ideally from the same batch. 1–2 discus → stress + lethal bullying. Buy them all at once, don't add them later one by one.

The drip method, 45–60 minutes: float the bag in the aquarium for 15 min to equalize temperature, then slowly drip aquarium water into the bag until you triple the volume. Transfer the fish with a net — do NOT pour the bag water into the aquarium.

Mandatory if you already have fish in the aquarium — 2–4 weeks in a separate 60–100L aquarium for observation. Optional if it's your first discus aquarium and they all arrive together from the same source.

Refusing food for 1–3 days, visible stress bars, sitting in a corner, pale colors. NORMAL. Abnormal = rapid breathing, swimming sideways, refusing food for over 5 days, visible lesions.

Minimum 4 weeks: week 1 — observation, week 2 — dual treatment Praziquantel + Metronidazole, week 3 — recovery, week 4 — check. For freshly imported Asians: 6–8 weeks. Below 4 weeks you miss the parasite cycles (Hexamita 14–28 days asymptomatic).

Beginners: Stendker (hard European water, health, 150–450 RON/piece) or a verified local breeder (identical water). Advanced: Asians through an EU importer or premium local breeders. Breeding: locals or Asians (Stendker are difficult to breed as a hobbyist).

DOUBLE polyethylene bags with a 1/3 water + 2/3 pure oxygen ratio, a 3cm polystyrene insulated box, a constant temperature of 28–30°C (heat pack in winter, cold gel in summer), total darkness. Stop feeding 24h before. Maximum 1 discus/bag for transport over 4h.

Yes, but through a slow 6-week transition: steps of at most +25 ppm TDS/week and +0.2 pH/week. You start at TDS 130–150 ppm (Asia water) and reach your water (250–400 ppm). A sudden transition = lethal osmotic shock, 40–80% mortality. You need an RO unit + remineralizer (Sera Mineral Salt).

Ask for 6 mandatory photo angles (left/right side, front, dorsal, ventral, head close-up) + 3 minutes of video (LIVE feeding, mid-water swimming, breathing close-up). 12 questions for the seller about water parameters, age, quarantine, DOA guarantee. For purchases >500 RON insist on a LIVE video call.

Refusing food on LIVE video (the definitive test) · white stringy feces (Hexamita) · breathing over 120/min · permanently intense stress bars · visible lesions (ulcers, HITH, dropsy) · the seller refuses LIVE video or doesn't know the parameters exactly · price 40%+ below market.

Temperature 29–30°C, ammonia 0 ppm, nitrite 0 ppm, nitrate below 20 ppm, pH 6.0–7.5 (stability > exact value). KH ≥2 dKH (avoid pH crash). GH 3–8 dGH.

Below 28°C the discus immune system collapses → Hexamita (internal parasites) and Ich (white spot) within 1–2 weeks. The high temperature is the definition of the species, not optional.

A liquid kit is mandatory (API Master Test Kit or JBL Test, NOT strips — ±20% error). Test ammonia + nitrite daily during cycling, then weekly. KH/GH monthly.

Yes in about 80% of cases, but always test your own supply first — tap water varies enormously by region. A dechlorinator is mandatory (chloramine does NOT evaporate). Hard tap water (TDS 400+) → a 40-50% RO mix is recommended; soft tap water (TDS under 250) is often fine directly. Always dechlorinate (Seachem Prime).

It depends on your tap water. Very hard supply (TDS 400+) → YES, a home RO unit usually pays for itself within 3-6 months. Moderately soft supply → buying RO water by the bottle is often cheaper. For breeding → effectively MANDATORY. A small hobbyist with one tank → buy RO water rather than installing a unit.

NO! Pure RO water (TDS 0, KH 0) = guaranteed pH crash. Mandatory: mix it with tap water (50/50 Bucharest) OR remineralize with Seachem Equilibrium + baking soda. RO water with no minerals = death within 24h.

A sudden drop >1.0 pH within a few hours, fatal in 24–48h. It happens when KH is below 1 dKH — the water no longer buffers the acids from respiration. Prevention: KH minimum 2 dKH AT ALL TIMES, monthly testing, baking soda on hand (0.5g/10L = +1 dKH). 100% unmineralized RO water = the #1 cause.

3 safe methods: 1) RO water mixed 50/50 with tap (Bucharest) — the most stable. 2) Aquarium peat in the filter (JBL Tormec ~50g/100L) — lowers it gradually 0.3–0.8. 3) Catappa leaves + mopani wood — a 0.2–0.5 drop. Do NOT use chemical 'pH down' — it causes shocks and a pH crash when you stop.

EMERGENCY: 1) 50% water change immediately with dechlorinated water at 29°C. 2) Seachem Prime double dose (5ml/100L) — neutralizes NH₃+NO₂ for 24-48h. 3) Turn on extra aeration. 4) Stop feeding for 48h. 5) Test again in 2 hours. Causes: filter cleaned in tap water, overpopulation, incomplete cycling.

Keeping Stendker/locals: 100–200 ppm. Breeding: 50–100 ppm. Wild (Heckel, Altum): below 50 ppm. Measure with a digital TDS meter (HM Digital TDS-3 ~60 RON, reliable for 3-5 years). Calibrate 1×/year with 342 ppm solution. Strips do NOT measure TDS correctly.

Yes, but only for advanced keepers (NOT beginners). Strict rules: KH minimum 3–4 dKH, a solenoid on a timer (off at night), extra aeration at night, weekly pH monitoring. A complete JBL/Aquario system 300-500 €. For 90% of keepers: low-tech without CO2 is the correct choice with Anubias/Java Fern/Echinodorus plants.

2–3 changes/week, 25–30% each. For fry: 50% daily. Don't change all the water at once. Use dechlorinated water at the aquarium temperature ±1°C.

Adults: 2 meals/day. Juveniles (under 10 cm): 3 meals/day. Fry: 4–5 meals/day. The 3-minute rule — as much as they eat without it falling to the bottom. One fasting day per week is recommended.

Beginners: premium discus pellets (Sera Discus, Tetra Discus) + frozen brine shrimp + frozen bloodworms. Avoid live food (parasite risk) and homemade beef heart in the first year (complicated).

The first 3 days after bringing them home = NORMAL. Over 5 days = a problem. Check: temperature 29°C? ammonia/nitrite = 0? bullying? Change the type of food, try frozen. Don't insist with large amounts.

A combination of 40% premium pellets (Tropical D-50/D-Allio Plus, Hikari Discus Bio-Gold, Tetra Discus, Sera Discus Granules) + 30-40% homemade beef heart mix + 20-30% frozen food (brine shrimp, krill, bloodworms). No single product — variety makes the difference.

Under 5 weeks: NO. Only brine shrimp nauplii + micro-pellets. From 5-8 weeks: only a very fine paste, alongside brine shrimp. Normal-sized pieces = lethal intestinal blockage.

2L warm water (28°C) + 60g coarse non-iodized salt (30g/L) + 1 teaspoon of brine shrimp eggs, strong aeration + 24h light. Harvest with a 100 micron net. Cost ~3-5 €/month for 50 fry.

Live tubifex = the #1 source of Hexamita outbreaks, flukes and heavy-metal contamination. 30-60% mortality within 2-4 weeks. Use frozen bloodworms or culture white worms (Enchytraeus) at home.

~140 RON/month for a complete diet: premium pellets (~30), 1kg homemade beef heart (~40), 200g frozen brine shrimp (~25), 100g krill (~20), 100g bloodworms (~15), amortized supplements (~10).

Natural astaxanthin from Antarctic krill (~300-500 mg/kg dry) + spirulina + carotenoids (paprika, red pepper). 1-2 meals/week with krill + spirulina integrated into the beef heart mix gives a visible boost in 4-6 weeks.

Stendkers are used to Stendker Original Granulat + frozen GoodHeart at the farm. A 4-8 week protocol: order Stendker Original Granulat (~43-89 RON), then a slow transition to Tropical D-50 or Hikari. Tricks: soaking in beef heart juice, a 24h fast, 30°C temperature.

Yes, it's mandatory. A 24h fast (Sunday recommended) cleans the digestive tract, prevents fatty liver, stimulates autophagy. Strict — not a single cube. Exceptions: fry under 3 months, breeders in conditioning, sick fish.

Yes. The ideal weekly combination: 40% pellets + 30-40% beef heart mix + 20% frozen (brine shrimp, krill, mysis) + 10% live food occasionally. In the same meal: frozen + pellets OK. On different days: live food or beef heart. Avoid mixing multiple frozen types at once — discus become picky.

Put the cube in a glass of aquarium water (28-30°C), wait 3-5 min, drain the red liquid (it pollutes the water), then feed. NEVER: microwave, hot water, thawing on the counter, or refreezing.

Opened pellets: max 6 months cool + dry (then 40-60% vitamin oxidation). Frozen beef heart mix: max 3-6 months at -18°C airtight (beyond = rancid fats). Commercial frozen food (blisters): 12-18 months sealed, max 60 days after opening. Liquid supplements: 6 months refrigerated after opening. Optimal storage: airtight Tupperware containers, a cool dry place, darkness, date labeling.

MANDATORY with homemade beef heart: JBL Atvitol (~35-50 RON, 3-5 drops/100g, 2×/week) + spirulina powder (~50-120 RON/250g, 1 tablespoon/kg of mix). OPTIONAL: fresh garlic (appetite stimulant + antiparasitic), astaxanthin/krill (red intensification), vitamins D3+E (breeders). NEVER: human vitamins (Centrum etc.) — TOXIC copper/zinc. Budget: ~50-80 RON/year for a complete setup.

Pellets: airtight Tupperware container + silica gel, a cool place (15-22°C), DARKNESS, away from perfumes. NOT in the fridge (condensation). Liquid supplements: fridge at 4°C after opening, sealed lid, darkness. Powder supplements: airtight container, darkness, dry, cool place. Monthly check: smell (rancid = throw out), color (changed = throw out), visible mold (throw out). Oxidized vitamins (invisible) = zero effect on the fish.

9 dark vertical bars on the body, NORMALLY present but temporarily visible under stress. A problem only if they stay dark for over 48h with no cause (new lights, moving, feeding).

Probably a subordinate (bullied). Check whether it eats, stays alone in a top corner, with clamped fins. Solution: rearrange the décor, more discus (dilutes aggression), or temporary separation.

Weeks 1–2: stress, partial refusal of food. Weeks 3–4: hierarchy + colors appearing. Month 2: stable routine. Month 3: fully normal behavior. See the detailed calendar.

If it's temporary (someone walked through the room, lights just turned on): normal, they come back. If it's permanent: test the water immediately, check the temperature, watch the breathing.

Top 5 killers: an uncycled aquarium (70%), temperature below 28°C (50%), an undersized filter (40%), cheap sick fish (60%), preventive treatments without a diagnosis (30%).

The first year: discus ONLY. After 1 year, options: Corydoras sterbai, cardinal tetra (careful — they can be eaten). NEVER: angelfish (parasites), barbs (nip), guppies (different requirements).

NO. Treatments with no symptom = they destroy the filter's bacterial colony → ammonia crisis. Treat only based on confirmed symptoms. At the first sign: test the water (90% of 'diseases' are bad parameters).

Common invisible causes: ammonia below 0.25 ppm (undetectable with strips), temperature dropping at night, old oxidized food, a bad source (fish already sick at purchase).