I would also suggest a FW dip and/or formalin bath before (or while) the fish is placed in QT. "Quick Cure", "Aquarium Solutions Ich-X" and "Kordon Rid-Ich Plus" all contain formalin - so that's better than nothing. If you can't find formalin, acriflavine is a suitable alternative. "Ruby Reef Rally" contains acriflavine if you can find that. See below for more info.
Freshwater Dip: Provides temporary relief for Brooklynella, Flukes, Marine Velvet disease (Amyloodinium); possibly even Ich & Uronema marinum (both unproven). Can be used to confirm the presence of Flukes.
How To Treat - Fill a bucket with RODI water, and use a heater to match the temperature to the water the fish is coming from. Aerate the water heavily for at least 30 minutes prior to doing the dip, then discontinue aeration while performing the dip. Fish aren’t overly pH sensitive for short durations like this, but you can squirt a little tank water into the dip just before the fish goes in to help bring it up.
Place the fish in the freshwater (FW) dip and observe closely. It is not unusual for them to freak out a little at first. Also, tangs are notorious for “playing dead” during a FW dip. The important thing is to watch their gills; they should be breathing heavily at all times during the dip. If breathing slows, it’s time to exit the dip. Dip the fish for no longer than 5 minutes. Multiple dips may be done, but it’s important to give your fish a day to recuperate in-between dips.
For flukes, use a dark (preferably black) bucket so you can see if tiny white worms fall out of the fish (especially out of the gills) at around the 3-4 minute mark. The worms will settle to the bottom, so you can use a flashlight to look for them there as well.
Pros - Provides temporary relief for a wide range of diseases in a chemical free environment. Can “buy you more time” until a proper treatment can be done.
Cons/Side Effects - Not a permanent “fix” for any disease, as FW dips are not potent enough to eradicate all of the parasites/worms afflicting the fish. Some fish can have an adverse reaction to a FW dip by appearing unable to maintain their equilibrium once returned to the aquarium. If this happens, hold the fish upright (using latex, nitrile or rubber gloves), and gently glide him through the water (to get saltwater flowing through the gills again). It is also a good idea to place the fish in an acclimation box until he appears “normal”.
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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 premixedbath 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.