Formalin: Treats Brooklynella and provides temporary relief for Marine Velvet disease (Amyloodinium). Also may be used as temporary relief, or even as an alternative treatment, for worms such as flukes and black ich.
How To Treat - Formalin is very interesting because its potential is not fully known. It is best administered in a bath solution for 30-45 minutes, following the dosage instructions on whatever bottle you use; or at 150 ppm if using "100% formalin" (ex. Formalin-MS). The bath should be done in a large glass bowl or container, and temperature should match the tank the fish is coming from. A bucket is not advised as plastic may absorb some of the medication and then leach it back out during future use. It is imperative that you heavily aerate the bath solution for at least 30 minutes before and also during treatment to compensate for oxygen depletion. The fish should be placed in a premixed bath solution. DO NOT add more formalin after the fish is already in the bath.
For Brooklynella, multiple baths may be required (so long as symptoms persist), but it’s important to give the fish a day to recuperate in-between baths. Formalin has also been used as alternative treatment for external worms such as flukes and black ich. However, at least 2 baths are required (7 days apart) for the same reason described when using Prazipro. For all of the above, post treatment, the fish should not be returned to the same tank/water he came from to prevent reinfection.
You can dose formalin directly in a quarantine tank, but this can be risky due to the harshness of formalin and how quickly it can deplete the water of oxygen. Providing additional gas exchange to the QT is a must! A fish being treated must be monitored closely and should be removed if showing signs of distress - this applies when treating in QT or in the bath solution.
Pros - Treats or provides temporary relief for a wide range of diseases. In some cases, formalin can “buy you more time” until a proper treatment can be done.
Cons/Side Effects - Formalin contains formaldehyde, a known carcinogen. Therefore, precautions must be taken when using it. Preventing your skin from coming in contact with it by wearing water proof gloves and not breathing in any fumes by wearing a face mask is highly recommended. Formalin also can be harsh on the fish and will quickly deplete oxygen from the water. In some areas, the purchase of formalin is prohibited.
