Aquarium Water Parameter Reference
Look up ideal water parameter ranges for any freshwater species. Compare pH, GH, KH, temperature, and nitrate thresholds across species.
Freshwater Species — Parameter Reference
All parameters verified against primary literature. Use as a baseline — individual tank and population variation exists. Always test with a calibrated liquid test kit, not test strips.
| Species | pH | Temp °F | GH dGH | Nitrate max | Difficulty |
|---|---|---|---|---|---|
| Betta Fish Betta splendens | 6–7.5 | 76–82 | 2–12 | 20 ppm | Beginner |
| Axolotl Ambystoma mexicanum | 7–8 | 57–68 | 7–16 | 20 ppm | Intermediate |
| Guppy Poecilia reticulata | 6.8–7.8 | 72–82 | 8–20 | 30 ppm | Beginner |
| Neon Tetra Paracheirodon innesi | 5.8–7 | 70–78 | 1–8 | 20 ppm | Beginner |
| Corydoras Catfish Corydoras spp. | 6–7.8 | 65–80 | 2–15 | 25 ppm | Beginner |
| Freshwater Angelfish Pterophyllum scalare | 6–7.5 | 76–84 | 1–10 | 20 ppm | Intermediate |
| Goldfish Carassius auratus | 6.5–8 | 50–72 | 8–20 | 20 ppm | Intermediate |
| Cherry Shrimp Neocaridina davidi | 6.5–7.5 | 65–78 | 6–15 | 20 ppm | Beginner |
| Bristlenose Pleco Ancistrus cf. cirrhosus | 6–7.5 | 73–82 | 3–15 | 20 ppm | Beginner |
| Kuhli Loach Pangio kuhlii | 5.5–7 | 73–82 | 1–8 | 20 ppm | Beginner |
| Neocaridina Shrimp Neocaridina davidi (various colour morphs) | 6.5–7.5 | 65–78 | 6–15 | 20 ppm | Beginner |
| Discus Symphysodon spp. | 5.5–7 | 82–88 | 1–6 | 10 ppm | Expert |
| Pea Puffer Carinotetraodon travancoricus | 6.5–7.8 | 74–82 | 4–15 | 15 ppm | Intermediate |
| Oscar Astronotus ocellatus | 6–7.5 | 74–81 | 5–15 | 20 ppm | Intermediate |
| Clownfish Amphiprion ocellaris | 8.1–8.4 | 75–82 | 15–20 | 10 ppm | Beginner |
| Molly Fish Poecilia sphenops / P. latipinna / P. velifera | 7–8.5 | 72–82 | 10–25 | 30 ppm | Beginner |
| Platy Fish Xiphophorus maculatus / X. variatus | 7–8.2 | 68–79 | 10–25 | 30 ppm | Beginner |
| Zebra Danio Danio rerio | 6.5–7.5 | 65–77 | 2–15 | 30 ppm | Beginner |
| Hillstream Loach Sewellia lineolata / Beaufortia leveretti (various) | 6.5–7.5 | 65–75 | 4–15 | 10 ppm | Intermediate |
| Rope Fish Erpetoichthys calabaricus | 6–7.5 | 72–82 | 3–15 | 20 ppm | Intermediate |
| Daphnia Daphnia magna | 6.5–8.5 | 64–75 | 5–20 | 40 ppm | Beginner |
| Scuds (Freshwater Amphipods) Hyalella azteca | 7–8.5 | 60–78 | 8–25 | 40 ppm | Beginner |
| Moina (Russian Red Daphnia) Moina macrocopa | 6.5–8.5 | 70–88 | 5–20 | 50 ppm | Beginner |
| Baby Brine Shrimp (BBS) Artemia salina | 7.5–8.5 | 78–82 | 20–40 | 50 ppm | Beginner |
| Microworms Panagrellus redivivus | 4–6 | 68–80 | 0–20 | 50 ppm | Beginner |
| Vinegar Eels Turbatrix aceti | 3–4.5 | 68–80 | 0–20 | 50 ppm | Beginner |
| Grindal Worms Enchytraeus buchholzi | 6–7.5 | 65–77 | 0–20 | 50 ppm | Beginner |
| White Worms Enchytraeus albidus | 6–7.5 | 50–68 | 0–20 | 50 ppm | Beginner |
| Banana Worms Panagrellus nepenthicola | 4–6 | 68–80 | 0–20 | 50 ppm | Beginner |
| Walter Worms Panagrellus silusiae | 4–6 | 60–78 | 0–20 | 50 ppm | Beginner |
| California Blackworms Lumbriculus variegatus | 6.5–8 | 50–72 | 4–20 | 40 ppm | Intermediate |
| Copepods Cyclops / Tigriopus spp. | 6.5–8.4 | 64–80 | 4–30 | 40 ppm | Intermediate |
| Seed Shrimp (Ostracods) Cypridopsis vidua | 6.5–8.5 | 60–80 | 6–25 | 40 ppm | Beginner |
| Detritus Worms Naididae spp. | 6–8.5 | 64–82 | 2–25 | 40 ppm | Beginner |
| Planaria Dugesia spp. | 6–8 | 60–80 | 2–20 | 40 ppm | Beginner |
| Hydra Hydra spp. | 6–8 | 60–80 | 2–20 | 40 ppm | Beginner |
| Rotifers Brachionus plicatilis | 7–8.4 | 70–82 | 8–35 | 40 ppm | Intermediate |
| Infusoria (Paramecium) Paramecium caudatum | 6–8 | 68–82 | 2–20 | 50 ppm | Beginner |
| Vorticella Vorticella spp. | 6–8.4 | 60–82 | 2–25 | 40 ppm | Beginner |
| Green Water (Phytoplankton) Chlorella / Scenedesmus spp. | 6.5–9 | 60–85 | 2–25 | 60 ppm | Beginner |
| Mystery Snail Pomacea bridgesii | 7–8 | 68–82 | 8–18 | 20 ppm | Beginner |
| Nerite Snail Neritina natalensis | 7–8.5 | 72–82 | 8–18 | 20 ppm | Beginner |
| Ramshorn Snail Planorbella duryi | 7–8 | 65–82 | 6–18 | 30 ppm | Beginner |
| Bladder Snail (Pest Snail) Physella acuta | 6.5–8.5 | 60–84 | 4–25 | 40 ppm | Beginner |
| Malaysian Trumpet Snail Melanoides tuberculata | 7–8.5 | 68–84 | 8–25 | 30 ppm | Beginner |
| Assassin Snail Clea helena | 7–8 | 72–82 | 8–18 | 20 ppm | Beginner |
| Java Moss Taxiphyllum barbieri | 5.5–8 | 59–86 | 2–20 | 40 ppm | Beginner |
| Duckweed Lemna minor | 6–8 | 59–86 | 2–20 | 60 ppm | Beginner |
| Black Beard Algae (BBA) Audouinella / Rhodophyta | 6–8 | 64–84 | 2–25 | 40 ppm | Advanced |
| Blue-Green Algae (Cyanobacteria) Cyanobacteria | 6–8.5 | 64–86 | 2–25 | 40 ppm | Advanced |
| Swordtail Xiphophorus hellerii | 7–8.2 | 72–80 | 10–25 | 30 ppm | Beginner |
| Cardinal Tetra Paracheirodon axelrodi | 4.5–6.5 | 73–81 | 1–6 | 20 ppm | Intermediate |
| Ember Tetra Hyphessobrycon amandae | 5.5–7 | 73–82 | 1–8 | 20 ppm | Beginner |
| Harlequin Rasbora Trigonostigma heteromorpha | 6–7.5 | 72–80 | 2–12 | 20 ppm | Beginner |
| Cherry Barb Puntius titteya | 6–7.5 | 73–81 | 2–15 | 20 ppm | Beginner |
| Tiger Barb Puntigrus tetrazona | 6–7.5 | 74–80 | 4–15 | 20 ppm | Beginner |
| Dwarf Gourami Trichogaster lalius | 6–7.5 | 76–82 | 4–15 | 20 ppm | Beginner |
| Pearl Gourami Trichopodus leerii | 6–7.5 | 77–82 | 3–12 | 20 ppm | Beginner |
| Honey Gourami Trichogaster chuna | 6–7.5 | 74–82 | 2–12 | 20 ppm | Beginner |
| German Blue Ram Mikrogeophagus ramirezi | 5.5–7 | 80–86 | 1–8 | 15 ppm | Intermediate |
| Bolivian Ram Mikrogeophagus altispinosus | 6–7.8 | 73–82 | 2–14 | 20 ppm | Beginner |
| Cockatoo Dwarf Cichlid Apistogramma cacatuoides | 5.5–7.2 | 75–84 | 1–10 | 15 ppm | Intermediate |
| Kribensis Pelvicachromis pulcher | 6–7.8 | 75–82 | 4–18 | 20 ppm | Beginner |
| Convict Cichlid Amatitlania nigrofasciata | 6.5–8 | 74–82 | 8–20 | 30 ppm | Beginner |
| Firemouth Cichlid Thorichthys meeki | 6.5–8 | 75–82 | 8–20 | 30 ppm | Beginner |
| Electric Yellow Cichlid Labidochromis caeruleus | 7.6–8.8 | 76–82 | 10–25 | 30 ppm | Intermediate |
| Otocinclus Otocinclus vittatus | 6–7.5 | 72–79 | 2–12 | 20 ppm | Intermediate |
| Siamese Algae Eater Crossocheilus oblongus | 6.5–7.5 | 75–81 | 5–18 | 20 ppm | Beginner |
| Clown Loach Chromobotia macracanthus | 6–7.5 | 77–86 | 5–15 | 20 ppm | Intermediate |
| White Cloud Mountain Minnow Tanichthys albonubes | 6–8 | 64–72 | 5–18 | 20 ppm | Beginner |
| Boesemani Rainbowfish Melanotaenia boesemani | 7–8 | 75–82 | 8–20 | 20 ppm | Beginner |
| Congo Tetra Phenacogrammus interruptus | 6–7.5 | 75–81 | 3–15 | 20 ppm | Intermediate |
| Rummynose Tetra Hemigrammus rhodostomus | 5.5–7 | 75–82 | 1–8 | 15 ppm | Intermediate |
| Silver Dollar Metynnis argenteus | 5.5–7.5 | 75–82 | 4–18 | 25 ppm | Intermediate |
| Denison Barb Sahyadria denisonii | 6.5–7.8 | 65–77 | 5–18 | 20 ppm | Intermediate |
| Paradise Fish Macropodus opercularis | 6–8 | 61–79 | 5–20 | 25 ppm | Beginner |
| Celestial Pearl Danio Danio margaritatus | 6.5–7.5 | 68–78 | 2–12 | 20 ppm | Beginner |
| Percula Clownfish Amphiprion percula | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Royal Gramma Gramma loreto | 8–8.4 | 72–80 | 7–12 | 10 ppm | Beginner |
| Yellow Tang Zebrasoma flavescens | 8–8.4 | 75–82 | 7–12 | 10 ppm | Intermediate |
| Blue Tang (Regal Tang) Paracanthurus hepatus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Advanced |
| Mandarin Dragonet Synchiropus splendidus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Advanced |
| Firefish Goby Nemateleotris magnifica | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Neon Goby Elacatinus oceanops | 8–8.4 | 72–80 | 7–12 | 10 ppm | Beginner |
| Yellow Watchman Goby Cryptocentrus cinctus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Banggai Cardinalfish Pterapogon kauderni | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Pajama Cardinalfish Sphaeramia nematoptera | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Six-Line Wrasse Pseudocheilinus hexataenia | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Flame Angelfish Centropyge loriculus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Intermediate |
| Coral Beauty Angelfish Centropyge bispinosa | 8–8.4 | 75–82 | 7–12 | 10 ppm | Intermediate |
| Lawnmower Blenny Salarias fasciatus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Green Chromis Chromis viridis | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Tomato Clownfish Amphiprion frenatus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Maroon Clownfish Premnas biaculeatus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Intermediate |
| Royal Dottyback Pictichromis paccagnellae | 8–8.4 | 75–82 | 7–12 | 10 ppm | Beginner |
| Copperband Butterflyfish Chelmon rostratus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Advanced |
| Foxface Rabbitfish Siganus vulpinus | 8–8.4 | 75–82 | 7–12 | 10 ppm | Intermediate |
| Diamond Goby Valenciennea puellaris | 8–8.4 | 75–82 | 7–12 | 10 ppm | Intermediate |
| African Dwarf Frog Hymenochirus boettgeri | 6.5–7.8 | 75–82 | 5–20 | 20 ppm | Beginner |
| African Clawed Frog Xenopus laevis | 6.5–8 | 65–77 | 5–25 | 30 ppm | Beginner |
| Fire-Bellied Toad Bombina orientalis | 6.5–7.8 | 65–78 | 5–20 | 20 ppm | Beginner |
| Chinese Fire-Belly Newt Cynops orientalis | 6.5–7.8 | 60–72 | 5–18 | 20 ppm | Intermediate |
| Spanish Ribbed Newt Pleurodeles waltl | 6.5–8 | 60–75 | 6–20 | 25 ppm | Beginner |
Ammonia and nitrite should always be 0 ppm in a cycled aquarium regardless of species.
Next useful step
Understanding Aquarium Water Parameters
Water parameters are the chemical and physical properties of your aquarium water that determine whether your fish can survive and thrive. The key parameters every aquarist needs to understand are pH, temperature, general hardness (GH), carbonate hardness (KH), and the nitrogen cycle compounds: ammonia, nitrite, and nitrate.
pH — Potential of Hydrogen
pH measures the acidity or alkalinity of water on a logarithmic scale from 0 to 14. A pH of 7.0 is neutral; below 7.0 is acidic; above 7.0 is alkaline. Each whole number represents a 10x change in hydrogen ion concentration — which is why a shift from pH 7.0 to 6.0 is far more significant than it appears.
Different species evolved in waters of vastly different pH. Blackwater Amazonian species like neon tetras and discus prefer pH 5.5–6.5, while Central American livebearers like swordtails and mollies thrive at pH 7.5–8.2. Keeping a fish at the wrong pH causes chronic osmotic stress, suppresses immune function, and shortens lifespan — even if the fish appears healthy in the short term.
General Hardness (GH)
General hardness measures the concentration of dissolved calcium and magnesium ions in your water. It is expressed in degrees of General Hardness (dGH) or parts per million (ppm), where 1 dGH = 17.9 ppm. Soft water has GH under 6 dGH; hard water is above 12 dGH.
GH matters because calcium and magnesium are essential minerals for fish physiology — bone development, nerve function, and osmoregulation all depend on them. Soft-water species like neon tetras and discus have kidneys adapted to extract these minerals efficiently from dilute water; hard-water species like swordtails and some cichlids require higher concentrations.
Carbonate Hardness (KH) and pH Stability
Carbonate hardness measures the concentration of carbonate and bicarbonate ions — the primary pH buffers in freshwater aquariums. KH directly determines how resistant your water is to pH changes. A tank with KH below 3 dKH is at serious risk of pH crashes (sudden acidic drops that can kill fish overnight), while a tank with KH above 6 dKH will maintain stable pH even with biological activity and CO₂ injection.
For most community aquariums, maintaining KH between 4–8 dKH is ideal for pH stability. Planted tanks injecting CO₂ need careful KH management — too low and pH crashes occur; too high and you cannot achieve the acidic pH some plants and species prefer.
Temperature
Aquarium fish are ectothermic — their body temperature matches the water temperature, and all metabolic processes are temperature-dependent. Temperature affects oxygen solubility (cold water holds more oxygen), metabolic rate, immune function, digestion speed, and reproductive behaviour.
Most tropical freshwater fish require 72–82°F (22–28°C). However, significant variation exists between species: German Blue Rams require 80–86°F; zebra danios tolerate down to 65°F; white cloud mountain minnows prefer 60–72°F. Mixing species with incompatible temperature requirements creates chronic stress for one or both groups.
The Nitrogen Cycle Compounds
Ammonia (NH₃/NH₄⁺), nitrite (NO₂⁻), and nitrate (NO₃⁻) are the products of the aquarium nitrogen cycle. In a properly cycled tank, beneficial bacteria convert fish waste (ammonia) to nitrite, then nitrite to nitrate. Nitrate is removed through regular partial water changes.
Ammonia is acutely toxic at any detectable concentration. Even 0.25 ppm causes gill irritation and immune suppression. In a cycled tank, ammonia should always read zero on a liquid test kit. Nitrite is similarly toxic, attacking hemoglobin and causing "brown blood disease." Nitrate is far less toxic but causes chronic problems above 20–40 ppm depending on species. Sensitive species like discus and German Blue Rams show disease symptoms at nitrate above 10–15 ppm.
Testing Your Water
Liquid test kits (API Master Test Kit, Salifert, Red Sea) are significantly more accurate than test strips. Test strips have wide error margins — particularly for pH and KH — that can give false confidence in unsafe water. For nitrate specifically, test strips routinely read 2–3x lower than actual concentrations.
Test your water weekly during the first three months of a new tank, then every 2–4 weeks in a stable, established aquarium. Always test after adding new fish, after treating disease, or after any unusual fish behaviour. Water parameters that look good on Monday can deteriorate significantly by Friday if bioload increases suddenly.
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