Ideal water parameters

Healthy ranges most keepers aim for. Species needs can be narrower; check each fish in the species guide.

Tropical freshwater

Parameter	Healthy	Acceptable
Ammonia	0	0–0.25
Nitrite	0	0–0.25
Nitrate	0–20	0–40
pH	6.5–7.8	6–8.2
Temperature	24–27 °C (75–81 °F)	22–29 °C (72–84 °F)
GH	4–12	2–18
KH	3–8	1–12
Phosphate	0–1	0–2

Planted

Parameter	Healthy	Acceptable
Ammonia	0	0–0.25
Nitrate	5–25	2–40
Phosphate	0.5–2	0.1–3
pH	6.2–7.4	5.8–8
KH	2–6	1–10
CO₂	15–30	8–35
Temperature	22–27 °C (72–81 °F)	20–29 °C (68–84 °F)
Nitrite	0	0–0.25
GH	4–10	2–15

Coldwater

Parameter	Healthy	Acceptable
Ammonia	0	0–0.25
Nitrite	0	0–0.25
Nitrate	0–20	0–40
pH	7–8	6.5–8.4
Temperature	16–22 °C (61–72 °F)	10–25 °C (50–77 °F)
GH	6–16	4–20
KH	4–10	2–14

Reef

Parameter	Healthy	Acceptable
Alkalinity	7–9.5	6–11
Calcium	400–450	360–480
Magnesium	1250–1400	1150–1500
Nitrate	2–10	0.5–25
Phosphate	0.03–0.1	0.01–0.2
Salinity	1.024–1.026	1.022–1.027
Temperature	25–26.5 °C (77–80 °F)	24–28 °C (75–82 °F)
pH	8–8.3	7.8–8.5
Ammonia	0	0–0.1
Nitrite	0	0–0.2

Marine fish-only

Parameter	Healthy	Acceptable
Ammonia	0	0–0.1
Nitrite	0	0–0.2
Nitrate	0–20	0–40
Salinity	1.02–1.025	1.018–1.026
pH	8–8.4	7.8–8.5
Temperature	24–27 °C (75–81 °F)	22–28 °C (72–82 °F)
KH	7–11	6–12
Phosphate	0–0.5	0–1

Brackish

Parameter	Healthy	Acceptable
Ammonia	0	0–0.25
Nitrite	0	0–0.25
Nitrate	0–20	0–40
Salinity	1.005–1.015	1.002–1.02
pH	7.5–8.4	7.2–8.6
Temperature	24–28 °C (75–82 °F)	22–29 °C (72–84 °F)
GH	10–20	6–25
KH	8–14	5–18

Pond

Parameter	Healthy	Acceptable
Ammonia	0	0–0.25
Nitrite	0	0–0.25
Nitrate	0–25	0–50
pH	7–8.5	6.5–9
KH	4–10	2–14
Temperature	10–25 °C (50–77 °F)	4–28 °C (39–82 °F)
GH	6–16	4–20