Here are some notes on the use traditional treatments such as chloramine T, formalin, BKC and salt. These are used as water treatments and are very valuable. If in any doubt speak to your veterinary surgeons, we are always happy to help other vets but sadly can’t routinely speak to pet owners.

I have provided some photos for parasite identification in the Fish parasites section.

These figures are used with trout and carp, we do not support them with ornamental species such as koi and goldfish.

This information is provided without any guarantee of safety or efficacy. The figures are ones I have used for many years but I can't take responsibility for what you do with them! Anyone reading these who isn't a client, please get your vet/adviser to check your calculations.

Chloramine T

This is one of the most useful chemicals available to the fish farmer. It has an effect against Myxobacteria, Costia, white spot and Gyrodactylus.

Dosage and administration
The following table of doses was suggested for systems with a 4 hour turnover, and where appropriate they can be repeated three times at 4 hour intervals.
Therapeutic dose
pH----Soft Water---Hard water
-------20 --------20

In general always err on the side of caution, start with 2ppm and increase carefully as necessary.

Contraindications, warnings etc
It is important to avoid contact with the skin or eyes so a mask and gloves should be use. The action of chloramine T is based on a slow breakdown to hypochlorous acid releasing oxygen and chlorine. Because of this it should not be used at the same time as other chemicals such as formalin or benzalkonium chloride.

BKC (benzalkonium chloride)

This is a blend of quaternary ammonium compounds specially selected for use in fish treatment. This family of chemicals are powerful disinfectants with an additional detergent action.

This family of chemicals are powerful disinfectants with an additional detergent action. they are particularly useful in treating external bacterial infections such as Bacterial Gill Disease (BGD) where Myxobacteria are multiplying within a film of mucus on the gills. The dual action is important since bacterial growth is inhibited and the mucus lifted off by the detergent effect. Other uses are as a net disinfectant where baths of others might be dangerous, or for reducing the bacterial loading in water containing fish with bacterial diseases such as Enteric redmouth.

Dosage and administration
In rapid turnover systems (5-10 minutes) up to 10ppm may be needed, with slower turnover sytems (30 minutes) 5 ppm may be used. For bath treatment in a static system 1ppm is used for 1 hour. In very slow earth ponds it may be necessary to use doses lower than 0.5ppm.
Repeat treatments are often used, to relieve the signs of gill disease and aid the fishes respiration by reducing the mucus coating.
Broodstock may be usefully treated since the chemical also has mild antifungal properties.

Contraindications, warnings etc
The toxicity of benzalkonium chloride is increased in soft water so treatment levels should be at least halved. If in doubt try lower doses first and increase as circumstances permit. It is reported than salmon intended for release should not be treated since the chemical inhibits the sense of smell and so can affect the ability of the salmon to return to its home river.


Formalin is a 35-40% solution of formaldehyde gas in water. It is used for the treatment of ectoparasitic infections of fish, particularly the protozoa - Costia, Trichodina, Chilodonella, it is also effective against the monogenetic skin and gill flukes (eg.Dactylogyrus and Gyrodactylus).

Assess gill condition first, formalin reduces oxygen levels so take care, aerate/oxygenate and be ready to cut treatment short.

Dosage and administration
The normal treatment level is:
1:6000 (167ppm) - 1:4000 (250ppm) for up to 1 hour

In most cases the lower level is preferred although the high dose may be required if it is being used against Epistylis, particularly if temperatures are low.

Used also as a 200ppm dip which should be aerated during use.
Contraindications, warnings
Formaln has a deoxygenating effect and toxicity may be seen during the course of treatment or for up to 24 hours afterwards. Fish with gill disease or anaemia should only be treated with great caution because they may not be able to get sufficient oxygen.


Salt has a number of uses:
• For the treatment of ectoparasitic infestations such as Costia and Chilodonella, particularly in fry.
• Treatment of alevins with coagulated yolks
• Cleaning the muddy flavour from otherwise marketable fish
• Reducing osmotic stress on individual high value fish

Dosage and administration
Alevins and small fry can be treated with 0.5% (5000 ppm) for 30 minutes, or 1% (10,000 ppm) for 6-10 minutes. Larger fish may be given progressively larger doses such that portion sized (8-10 oz) fish can be treated with 3% salt (30,000 ppm) until they show signs of distress.
For treatment of high value fish to reduce osmotic stress a level of 0.15% (1500 ppm) on day 1, can be built up to 0.3% (3000 ppm) over 3 days, if any signs of distress are seen the solution should be diluted.

As a general rule it is recommended that alevins and fry under 100/lb (5g) should not be exposed to over 1% (10,000 ppm) sodium chloride, and that fish under 5/lb should not be exposed to levels greater than 2% (20,000 ppm).
Protect from damp.