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From £10.99

Formaldehyde Bulk

Anti-Parasite Treatment for Koi

Treats: White Spot, Trichodina, Costia, Chilodonella.

When to Use:

  • Formaldehyde 30% is effective against protozoan parasites. It is especially useful in treating parasites because of its ability to penetrate mucus and reach the parasites that would otherwise be protected from other bath treatments.
  • Formaldehyde can also be used in combination with Malachite Green to treat protozoan parasites.


  • Switch off UV for at least 5 days.
  • Wait 7 days after the final dose before treating with a different medication.
  • If you feel that a repeat dose is necessary, check your diagnosis carefully, a different medication may be more suitable.
  • Can be used with Malachite Green to treat parasites.


Use when water temperatures are above 30oC.

View our medicinal treatment rules


Available in the following variations:

250ml, 500ml, 1 Litre & 2.5 Litre

Stockist Finder

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Let us calculate your dosage for you!

To make the process of using our products even easier this handy dosage calculator tells you the amount you will need to put into your system. Please ensure you also read the instructions and warnings that are written on the bottle/pack label.

I know my system's measurements and want to:

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Dosage calculator

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* Always follow the instructions on the label. This calculator is intended to be used only as a guide to how much product you need to buy to treat your system. It does not take account of displacement caused by gravel, rocks and ornaments etc and does not include the volume of any external filtration system. NT Laboratories Ltd. will not accept any responsibility for inaccuracies or misuse of this guide.