Fish aquarium
Two living worlds: a planted office tank and a hardy outdoor pond
T01 office planted tank — at a glance
| Item | Value |
|---|---|
| Size | 31 × 15 × 12 in (79 × 38 × 30 cm) |
| Water | 91 L gross · ~70 L real (2 in substrate) |
| Style | Low-tech jungle + riparium (plants out of the top) |
| Kit now | HOB filter, LED, thermometer, 2 plant baskets; no heater |
| State 10-13 | No fish, green water, thread algae, sword yellowing |
| Light | 6–7 h on a timer; no window sun on glass |
| Target | 24–25 °C · pH 6.5–7.5 · NH3 0 · NO2 0 · NO3 < 20–40 |
T02 outdoor tank — at a glance
| Item | Value |
|---|---|
| Size | 10 × 2 × 2 ft (305 × 61 × 61 cm) |
| Water | 1,133 L gross · ~1,000 L (6 cm freeboard) |
| Climate | NCR: winter nights ~5 °C air, summer 45 °C, monsoon |
| Threats | Heat, sun, rain overflow, birds, cats, mosquitoes |
| Pump | Turnover ≥ 250 L/h goldfish · ≥ 500 L/h koi |
| Shade | ⅓–½ surface under plants + shade sail at noon |
| Cover | Bird/cat net or mesh lid; overflow pipe with mesh |
T01 stocking — soft, small, peaceful (~70 L)
| Animal | Qty | Size | °C · pH | Zone · behaviour | Compatibility |
|---|---|---|---|---|---|
| Neon tetra ★ | 20 | 3 cm | 21–25 · 6–7.5 | M · tight blue school | Eats shrimp babies; buy active fish, no pale patches |
| Honey gourami | 3 (1♂ 2♀) | 5 cm | 22–28 · 6–7.5 | T · curious, begs at glass, bubble nests | Indian native; 1 male only; eats shrimplets |
| Pygmy corydoras | 10 | 3 cm | 22–26 · 6.4–7.4 | B/M · group hovers, sifts lightly | Does not dig; needs small sinking food |
| African dwarf frog | 2 | 4–6 cm | 23–26 · 6.5–7.8 | B · surfaces to breathe, the clown | ! Not clawed frog (separate fingers). Slow, near-blind: pipette-feed |
| Otocinclus | 4 | 4 cm | 21–26 · 6–7.5 | Glass/leaves · algae-film grazer | Mature tank only; add algae wafers |
| Amano shrimp ★ | 6 | 5 cm | 20–27 · 6.5–7.5 | All · best thread-algae eater | Larvae need brackish: no breeding |
| Cherry shrimp | 20 start | 2–3 cm | 18–28 · 6.5–8 | Plants · breeds freely | Babies survive only in moss/carpet |
| Nerite snail | 3 | 2–3 cm | 22–27 · 7–8.5 | Glass/rock · strong algae grazer | Needs GH ≥ 6; eggs never hatch in freshwater |
| Mystery snail | 1 | 5 cm | 20–28 · 7–8 | All · eats leftovers, dead leaves | Pink clutch above waterline; remove to stop 100 babies |
| Shared target | — | — | 24–25 · 6.8–7.4 | 3 layers filled: T/M/B | No digger in list: carpet stays put |
T01 add in this order (6–8 weeks)
| Week | Add | Check first |
|---|---|---|
| 0 | Fix light, blackout, top up | Re-cycle: 2 ppm NH3 → 0 in 24 h |
| 1 | Floaters + basket houseplants | Green water clearing |
| 2 | Amano 6 · Nerite 3 | NH3 0 · NO2 0 |
| 4 | Otocinclus 4 · Cherry 20 | Algae film present; GH ≥ 6 |
| 5 | Neon tetra 10 | Heater holds 24–25 °C |
| 6 | Neon 10 · Pygmy cory 10 | Tests 0 / 0 after 1 week |
| 8 | Honey gourami 3 · ADF 2 · Mystery 1 | Quarantined 2–4 wk in a tub |
T01 never add
| Animal | Why |
|---|---|
| Goldfish | Coldwater, messy, uproots, outgrows 70 L |
| Angelfish, big gouramis | Eat neons and shrimp |
| Tiger barb | Fin-nipper |
| Cichlids, crayfish | Dig, uproot, kill shrimp |
| Common/bristlenose pleco, SAE | Grow 15 cm+, big waste |
| Bronze/panda cory, loaches | Dig up the carpet |
| African clawed frog | Grows big, eats fish |
| Betta | Hunts the shrimp colony |
T01 animals






T02 stocking — hardy, NCR year-round (~1,000 L)
| Animal | Qty / 1,000 L | Adult | Range °C · hardiness | NCR verdict | Notes |
|---|---|---|---|---|---|
| Comet goldfish ★ | 6–8 | 25–30 cm | Cold-hardy; stress > 30 · ●●● | Year-round | Rule: 1–3 kg fish per 1,000 L; plan for adult size |
| Shubunkin | in the 6–8 | 25–30 cm | As comet · ●●● | Year-round | Calico comet; mixes perfectly with comets |
| Koi | 1–2 max | 60 cm+ | Best 15–25; stress > 27 · ●●● | ! Heat risk, outgrows | Use instead of 2 comets; rehome past ~40 cm |
| Zebra danio ★ | 15–20 | 5 cm | Wild water 12–39 · ●●● | Year-round | Indian native; fast, eats larvae |
| Rosy barb | 10–12 | 6–8 cm | Comfort 14–28 · ●●● | ! Borderline Jan | N-Indian native; keep a heated tub ready |
| Giant danio | 8–10 | 10 cm | Min ~18 (care sheets) · ●●● | ! Mar–Oct only | Indian native; winter indoors |
| Blue panchax | 6 | 5–8 cm | Tropical; cold limit unknown · ●●● | ! Summer trial | Native killifish, proven larva-eater (Hora & Nair) |
| Guppy, Gambusia | 0 | 3–6 cm | Guppy suffers < 15–18 | ! Avoid | NBA lists both invasive alien; never release |
| Fancy goldfish (oranda etc.) | 0 | 15 cm | Weak swimmers | Avoid outdoors | Out-competed; birds take them |
| Native pond/ramshorn snails | Self-arrive | 1–4 cm | ●●● | OK | Come on plants; graze algae; goldfish thin them |
T02 plan options
| Plan | Stock | Bioload |
|---|---|---|
| A ★ Goldfish pond | Comet/shubunkin 8 + zebra danio 15 + snails | ●●● |
| B Koi accent | Koi 2 + comet 3 + zebra danio 15 | ●●● needs 500 L/h |
| C Native stream | Zebra 20 + rosy barb 12 (+ giant danio summer) | ●●● |
T02 mosquito control
| Method | Note |
|---|---|
| Fish ★ | Any healthy fish clears larvae; danios fastest |
| Flow | Pump or air keeps surface moving |
| Floaters thinned | Dense mats hide larvae from fish |
| Bti dunk | Bacterial larvicide, fish-safe; for fishless pots |
| ! Gambusia | Used by Delhi MCD, but invasive: never |
T02 build and safety rules
| Rule | Detail | Rule | Detail |
|---|---|---|---|
| Shade | Shade sail 11 am–4 pm; lily/lotus pads cover ⅓–½ | Top-up | Dechlorinated; ≤ 10% at a time; temp-matched |
| Oxygen | Air pump on UPS; aerate night + dawn (lowest O2) | Pots | Plants in pots, gravel on top; koi/goldfish dig |
| Overflow | Pipe with mesh at 6 cm freeboard; rain can't flush fish | Thermometer | Read daily in May–Jun and Dec–Jan |
| Predators | Net or mesh lid vs herons, kingfishers, crows, cats | Depth | Keep full 55 cm: deep water swings less |
| Filter | Bio media rinsed in pond water only, never tap | Leaves | Net out daily; rotting leaves → NH3 |
T02 NCR season calendar
| Months | Air | Water risk | Do |
|---|---|---|---|
| Dec–Jan | Nights ~5 °C | Cold, slow fish, tropicals die | Goldfish/koi: feed little, stop below ~10 °C water; tropicals indoors; lid on at night |
| Feb–Mar | Warming | Algae bloom as sun returns | Restart feeding above ~10 °C; split/repot lilies + lotus; add shade early |
| Apr–Jun | 40–45 °C | > 30 °C water, low O2, evaporation | Shade + full aeration; feed less, wheat-germ food above 28 °C; slow cool top-ups |
| Jul–Sep | Monsoon | Overflow, pH/KH drop, runoff, mosquitoes | Keep overflow clear; test KH; no garden fertiliser runoff; lotus flowers |
| Oct–Nov | Mild | Best season | Stock fish, plant, clean filter, net leaves |
T02 animals and plants






Indoor plants (T01)
| Plant | Type | Light | Growth | Care | Flag |
|---|---|---|---|---|---|
| Dwarf sagittaria | Carpet | M | ●●● runners | T01's grass; pull thread algae weekly | — |
| Java moss | Carpet/epiphyte | L | ●●● | Tie on wood/rock; shrimp nursery | ★ shrimp |
| Amazon sword | Rosette | M | ●●● big | Heavy root feeder: root tabs 2–3 mo | Old leaves yellow = N/K low |
| Crypt wendtii | Rosette | L–M | ●●● | Mid-ground; may melt after moving | Regrows from roots |
| Vallisneria | Rosette, runners | L–M | ●●● | Background ribbons | ! Melts with liquid carbon |
| Hygrophila polysperma | Stem | L–M | ●●● | Indian native; nitrate sponge | Trim weekly |
| Water wisteria | Stem | L–M | ●●● | Background; Indian region | Trim + replant tops |
| Rotala rotundifolia | Stem | M | ●●● | Pink tips under stronger light | Trim weekly |
| Java fern | Epiphyte | L | ●●● | Tie to wood | ! Never bury rhizome |
| Anubias | Epiphyte | L | ●●● | Tie to wood, shade | Spot algae in strong light |
| Salvinia minima / red root floater | Floating | M | ●●● | Shades tank, starves green water | Scoop excess; not S. molesta |
| Brazilian pennywort | Float/emersed | M | ●●● | Trails over rim | Grows above water happily |
| Pothos, syngonium, peace lily | Emersed houseplant | Room | ●●● | Basket, roots in water, all soil washed off | ★ best nitrate filter |
Outdoor plants (T02)
| Plant | Type | Sun | Depth / pot | Care | Flag |
|---|---|---|---|---|---|
| Lotus (bowl/dwarf) ★ | Deep-water | FS | 15–22 cm over soil; wide pot | Heavy loam, no drain holes; flowers Jul–Sep; dormant winter | Large types want 40–60 cm |
| Tropical water lily | Deep-water | 6–7 h FS | 20–30 cm over soil; 35–45 cm pot | Crown centred; fertiliser tab monthly in season | Tropicals suit India; day + night bloomers |
| Hardy water lily | Deep-water | 6–7 h FS | 13–25 cm over soil | Rhizome at pot edge, tip out | Better for hills; OK in NCR winter |
| Umbrella palm (Cyperus) | Marginal | FS–PS | Pot on brick, rim at surface | Tall vertical accent | Divide yearly |
| Colocasia / taro | Marginal | FS–PS | Roots wet, crown above | Big leaves shade water | Cut back in winter |
| Water spinach (kalmi) | Marginal/creeper | FS | Edge, trailing | Indian native, edible, nitrate sponge | ! Fast spreader; trim |
| Azolla | Floater | FS–PS | Surface | Native fern; fixes nitrogen; red in sun | Scoop half when full |
| Duckweed (Lemna) | Floater | FS–PS | Surface | Goldfish food | ! Hard to ever remove |
| Water lettuce (Pistia) | Floater | PS | Surface | Shades, eats nutrients | ! Invasive in India; contained only |
| Water hyacinth / Salvinia molesta | Floater | — | — | — | ! Never: worst invasives |
| Hornwort (Ceratophyllum) | Oxygenator | FS–PS | Free-floating | No roots; goldfish spawn on it | ★ Native, tough |
| Hydrilla / Vallisneria spiralis | Oxygenator | FS–PS | Weighted pots | Native; fish nibble | Thin monthly in summer |
Plant rules (Walstad)
| Rule | Why |
|---|---|
| Plants are the filter | Take NH4 before bacteria do |
| Floaters + emersed win | Air CO2 → beat algae |
| Fish food = fertiliser | Light stock, no CO2 needed |
| Soil option: 2.5 cm soil + 2.5 cm gravel | Feeds roots for years |
| Many fast plants on day 1 | Starve algae from the start |
| Midday light "siesta" | Lets CO2 rebuild |
| Don't vacuum planted gravel deep | Roots + bacteria live there |
| T01 heavy stock → keep weekly WC | Walstad's rare WC = light stock only |
Nitrogen cycle
| Step | What happens |
|---|---|
| 1 | Waste, food, dead leaves → NH3 |
| 2 | Bacteria: NH3 → NO2 |
| 3 | Bacteria: NO2 → NO3 |
| 4 | Plants eat NH4/NO3; WC removes rest |
| Cycle | 3–6 wk; done when 2 ppm NH3 → 0/0 in 24 h |
| Speed-up | Used sponge from a healthy tank, bottled bacteria |
| T01 now | Long fishless spell: bacteria may have starved, re-test |
| ! | Rinse sponge in tank water, never tap |
Water parameters
| Parameter | T01 target | T02 target | Why | If off |
|---|---|---|---|---|
| NH3 ammonia | 0 | 0 | Burns gills; worse in warm, alkaline water | 30–50% WC, stop feeding 1 day |
| NO2 nitrite | 0 | 0 | Blocks blood oxygen | WC; wait for bacteria |
| NO3 nitrate | < 20–40 | < 40 | Stress, feeds algae | More plants, regular WC |
| Temp °C | 24–25 stable | 10–30, shade in summer | Swings kill more than numbers | Heater (T01); shade + air (T02) |
| pH | 6.5–7.5 | 7–8, stable | Don't chase pH | Stable source water |
| GH / KH | 4–10 / 2–6 | Moderate / ≥ 3 | Shells, moults / pH buffer | Mix RO + tap; rain lowers KH |
| TDS | 150–300 | 150–400 | Quick hardness proxy | RO for soft, tap for hard |
Maintenance schedule
| When | T01 indoor | T02 outdoor |
|---|---|---|
| Daily | Temp, count animals, feed what goes in 2 min | Temp (summer/winter), count fish, check net + pump |
| Weekly | 20–30% WC, wipe glass, trim, pull thread algae | 10–20% WC (dechlorinated), skim leaves, thin floaters |
| Fortnightly | Test NH3/NO2/NO3/pH (weekly first 2 months) | Test NH3/NO2/pH; KH after heavy rain |
| Monthly | Squeeze sponge in tank water; prune stems | Rinse pump pre-filter; lily/lotus fertiliser tab |
| 2–3 months | Root tabs at sword + crypts; check heater, timer | Cut dead pads; repot crowded lilies (Feb–Mar) |
| Twice a year | Replace half the sponges, never all | Full clean before Apr heat; check net + overflow |
Algae fixes
| Type | Cause | Fix |
|---|---|---|
| Green water | Sun + spare nutrients | Block sun, 3–4 day blackout, floaters |
| Thread/hair | Strong light, new tank | Toothbrush twirl, Amano, 6 h light |
| Brown diatoms | New tank, silicates | Wipe; otos + nerites; fades |
| Green spot | Strong light | Scrape; nerites |
| Black beard | Unstable CO2, old waste | Trim; liquid carbon spot-dose |
| Blue-green slime | Poor flow, dirty floor | Siphon, flow, blackout |
| T02 pea soup | Full sun | Shade + lilies; fish fine, don't panic |
Health quick check
| Sign | Likely | Do |
|---|---|---|
| Salt-grain spots | Ich | Hospital tub, raise heat slowly 28–30 °C |
| Ragged fins | Fin rot | WCs, fix cause |
| Gasping at top | NH3 or low O2 | Big WC, air stone, stop feeding |
| Pinecone scales | Dropsy | Isolate; often fatal |
| Neon pale, alone | Neon disease | Remove; no cure |
| Shrimp die moulting | GH/WC shock | Smaller, slower WCs |
| ! Copper meds | Kill shrimp, snails, frogs | Treat in a separate tub only |
Start kit (₹, Amazon.in 13-Oct-2026)
| Item | ₹ | For | Item | ₹ | For |
|---|---|---|---|---|---|
| Heater 100 W (Sobo / Eheim) | 899 / 7,131 | T01 winter | Algae wafers (Hikari) | 400 | Otos, snails |
| API Freshwater Master kit | 4,700 | Both | Frozen bloodworm | 378 | Frogs, corys |
| GH + KH kit | 1,000–1,500 | Both | Feeding pipette | 244 | Frogs |
| TDS pen | 300–700 | Both | Root tabs + liquid fert | 500–1,300 each | T01 plants |
| Seachem Prime | 1,397 | Both | Battery air pump / UPS | 800–3,000 | Power cuts |
| Plug timer | 629 | T01 light | Gravel siphon + bucket | 300–800 | WCs |
| Auto-feeder | 997 | Holidays | Floaters, stems, moss | 100–300 / portion | T01 |
| Micro pellets (Hikari) | 406 | T01 fish | Pond pump, shade sail, net, pond pellets | ₹? | T02 |
Feeding
| Who | Food | How |
|---|---|---|
| Neons, gourami | Micro pellets, crushed flake | 1–2×/day, 2 min |
| Corys, frogs | Sinking pellets, frozen bloodworm | Pipette to frogs |
| Otos, snails | Algae wafers, blanched veg | 2–3×/week |
| Goldfish, koi | Floating pellets; wheat-germ when hot | 1–2×/day > 10 °C |
| All | One fast day a week | Holidays: auto-feeder |
Breeding basics
| Animal | What happens |
|---|---|
| Cherry shrimp B | Berried ~3–4 wk; babies hide in moss |
| Mystery snail | Pink clutch above waterline; remove if unwanted |
| Nerite snail | White dots on wood; never hatch |
| Pygmy cory | Eggs on glass after cool WC; mostly eaten |
| Honey gourami I | Male gold, dark throat, bubble nest; fry need infusoria |
| Amano shrimp | Larvae need brackish: no breeding |
| Goldfish (T02) | Spawn on hornwort in spring; adults eat eggs |
Learn in this order
| Step | Learn → do |
|---|---|
| B 1 | Nitrogen cycle → test T01, log readings |
| B 2 | Water sources → TDS of tap, borewell, RO |
| B 3 | Light + algae → timer, shade, blackout |
| B 4 | Plants → floaters + basket houseplants |
| I 5 | Stocking + quarantine → crew, then fish |
| I 6 | T02 build → shade, net, pump, goldfish |
| I 7 | Lotus + lily care → pot, feed, divide |
| A 8 | Breeding → shrimp colony, gourami fry |
Buying checks
| Check | Why |
|---|---|
| Shop tanks clean, no dead fish | Disease comes home with the fish |
| Active, full colour, fins open | Neon farm stock can be weak |
| Dwarf frog: webbed front feet | Clawed frog has separate fingers |
| Quarantine 2–4 wk, sponge + heater tub | Stops ich and neon disease |
| Buy Oct–Nov or Feb–Mar | Mild weather, less transport shock |
Power cuts and holidays
| Event | Do |
|---|---|
| Cut > 2 h | Rinse filter media in tank water before restart |
| Any cut | Battery air pump or UPS keeps O2 |
| 3–5 days away | Healthy adult fish skip food safely |
| Longer | Auto-feeder, tested 1 week before |
| Office boy | One-page plan: feed, light, check, whom to call |
| T02 in summer | Shade + air matter more than food |
Avoid
| Mistake | Instead |
|---|---|
| Fish before cycling | Test 0/0 first |
| Overfeeding | 2 min, 1 fast day |
| Window sun on T01 | Shade + timer |
| No heater in winter | 100 W thermostat |
| Filter rinsed in tap | Old tank water |
| All fish at once | Stage over 6–8 wk |
| Hyacinth/Pistia/Gambusia outdoors | Native plants + fish |
| Unshaded T02 in May | Sail + pads + air |
























