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Summary :

Water mixing volumes for a target hardness Magnesium level calculator Total hardness (TH - GH) calculation from Calcium and Magnesium levels Dissolved CO₂ level calculator

Water Mixing Volumes for a Target Hardness

Enter the hardness (TH or GH) of your tap water, the desired total water volume, and the target hardness (TH/GH). (Reverse osmosis water is assumed to have TH and GH = 0.)

GH/TH tap water: °f	Final volume: liters of water	GH/TH target final: °f
You need to mix liters of RO water and liters of tap water.

Magnesium Level Calculator

Enter either TH or GH, followed by the Calcium level. (TH/GH is very high in saltwater, so this formula is not recommended for marine aquariums.)

TH °f
or
GH °all

mg/l Calcium

mg/l Magnesium

Total Hardness (TH - GH) Calculation from Calcium and Magnesium Levels

Enter the Calcium and Magnesium levels to calculate the corresponding TH and GH values. (Although this formula remains valid in saltwater, it has limited practical use there.)

mg/l Calcium

mg/l Magnesium

TH °f
or
GH °all

Dissolved Level Calculation de CO₂

Enter the KH and pH values. (pH cannot be lower than 4.5. Water temperature is assumed to be 25 °C.)

KH °all

mg/l CO₂

The table below estimates dissolved CO₂ concentration based on KH and pH values.
Warning: when filtering over peat or with a newly installed active aquasoil substrate, this chart should not be used!

KH / pH	6	6.1	6.2	6.3	6.4	6.5	6.6	6.7	6.8	6.9	7	7.1	7.2	7.3	7.4	7.5	7.6	7.7	7.8	7.9	8
1	30	24	19	16	12	10	8	6	5	4	3	3	2	2	2	1	1	1	1	1	1
2	60	48	38	31	24	19	16	12	10	8	6	5	4	4	3	2	2	2	1	1	1
3	90	72	57	46	36	29	23	18	15	12	9	8	6	5	4	3	3	2	2	2	1
4	120	96	76	61	48	38	31	24	20	16	12	10	8	7	5	4	4	3	2	2	2
5	150	120	95	76	60	48	38	30	24	19	15	12	10	8	6	5	4	3	3	2	2
6	180	143	114	91	72	57	46	36	29	23	18	15	12	10	8	6	5	4	3	3	2
7	210	167	133	106	84	67	53	42	34	27	21	17	14	11	9	7	6	5	4	3	3
8	240	191	152	121	96	76	61	48	39	31	24	20	16	13	10	8	7	5	4	4	3
9	270	215	171	136	108	86	68	54	43	34	27	22	18	14	11	9	7	6	5	4	3
10	300	239	190	151	120	95	76	60	48	38	30	24	19	16	12	10	8	6	5	4	3
11	330	263	209	166	132	105	83	66	53	42	33	27	21	17	14	11	9	7	6	5	4
12	360	286	228	181	144	114	91	72	58	46	36	29	23	19	15	12	10	8	6	5	4
13	390	310	247	196	156	124	98	78	62	50	39	31	25	20	16	13	10	8	7	5	4
14	420	334	266	211	168	133	106	84	67	53	42	34	27	22	17	14	11	9	7	6	5
15	450	358	284	226	180	143	114	90	72	57	45	36	29	23	18	15	12	9	8	6	5
16	480	382	303	241	192	152	121	96	77	61	48	39	31	25	20	16	13	10	8	7	5
17	510	406	322	256	204	162	129	102	81	65	51	41	33	26	21	17	13	11	9	7	6
18	540	429	341	271	215	171	136	108	86	68	54	43	35	28	22	18	14	11	9	7	6
19	570	453	360	286	227	181	144	114	91	72	57	46	36	29	23	19	15	12	10	8	6
20	600	477	379	301	239	190	151	120	96	76	60	48	38	31	24	19	16	12	10	8	6
Values between 0 and 15 mg/l of CO₂ are insufficient.
Values between 15 and 40 mg/l of CO₂ are optimal.
Values between 40 and 100 mg/l of CO₂ are dangerous to very dangerous.
Values above 100 mg/l of CO₂ are lethal.

These values and target ranges are indicative only, as lightly planted aquariums theoretically require less CO₂ (lower end) than heavily planted setups such as Dutch-style aquariums (upper end).