Triphenylmethane dyes in the aquarium hobby

All of these compounds are effective against parasites, ciliates, protozoa, fungi and in some cases bacteria. Some compound from this group is therefore probably always contained in a preparation against spot disease.

Caution: All of the following compounds, with the exception of methylene blue, are suspected of being carcinogenic to be carcinogenic!

Malachite green

R¹ = -CH₃, R² = -H

IUPACN,N-Dimethyl-4-[p-(dimethylamino)-diphenylmethylene]-2,5-cyclohexadienylideneammonium chloride or oxalate (1/2 eq.)
C.I.: 42000; Basic Green 4 / also diamond green called
Molecular formula: C₂₃H₂₅N₂Cl (MW: 364.92) or C₂₄H₂₅N₂O₂ (MW: 373.47)

Brilliant green

R¹ = -CH₂CH₃, R² = -H

IUPAC: N,N-Diethyl-4-[p-(diethylamino)-diphenylmethylene]-2,5-cyclohexadienylideneammonium hydrogen sulfate
C.I. 42040; Basic Green 1 / also ethyl green or malachite green G called
Molecular formula: C₂₇H₃₄N₂O₄S (MW: 482.64)

Crystal violet

R¹ = -CH₃, R² = -N(CH₃)₂

IUPAC: N,N-Dimethyl-4-[p,p'-bis(dimethylamino)-diphenylmethylene]-2,5-cyclohexadienylidene ammonium chloride
C.I.: 42555; Basic Violet 3 / also Hexamethylpararosaaniline chloride or methyl violet 10B called
Molecular formula: C₂₅H₃₀ClN₃ (MW: 407.98)

Methylene blue

IUPAC: 3,7-Bis(dimethylamino)phenothiazinylium chloride
C.I. 52015; Basic Blue 9 / tetramethylthionine chloride, methylthionium chloride
Molecular formula: C₁₆H₁₈ClN₃S (MW: 319.85)

Effect

Against Costia, Chilodonella, Trichodina, Saprolegnia, Cryptobia and Trypanosoma. Also popular for prevention and against spawn fungus.
The 1 % solution (10 g / litre) or, if less is required, the 0.1 % solution (1 g / litre) in water is used. The solution can only be kept for a long time if protected from light.

Dosage