The Free On-line Aquaculture Dictionary
Hydrogen sulphide toxicity with pH
pH
% H2S
5.0
99
5.5
97
6.0
91.1
6.5
76.4
7.0
50.6
7.5
24.4
8.0
9.3
8.5
3.1
9.0
1.0
Most species are extremely sensitive to H2S gas, toxic levels are given below;
Concentration
Effect
0.002 - 0.4mg/l
Sublethal effects, gill damage, depending on species*
0.01 - 5.3 mg/l
Lethal depending on species*
*Generally the lower the organic loading of the fishes natural habitat, the more sensitive it is e.g. salmonids are more sensitive than carps