if one fish has ich you need to treat ALL of them. You now have ich in your tank and any new fish will also get ich. The only way to get the ich out of the tank is to leave it fallow (no fish) for 72 days. This removes the parasites food source and it dies.
Any fish you have, should be treated in a hospital tank. I’d recommend a 20-29 gallon if there are a lot of fish, with just one or two small fish you can get away with a ten gallon. I use a sponge filter (I’d use 2 in a 20 or 29 gallon tank). These are cheap and run on an air pump. Since you need it immediately. I’d soak the sponge in a bottled saltwater bacteria like Dr Tim’s For a couple hours before adding it. Use it straight no dilution. This helps jumpstart the colonization. Add some PVC pipe connectors, elbows and Ts, for the fish to hide in and add a small heater. I’d suggest a seaChem ammonia alert badge so you can monitor ammonia in real time.
To treat for ich you need copper or hyposalinity. Ich attack will NOT kill ich. I personally prefer hyposalinity as it is easier on the fish.
for hyposalinity You need to slowly lower the salinity (over a couple days) to 1.009. You need a calibrated refrectometer for this, no hydro meters, the salinity must stay at 1.009 for 4 weeks. If it goes higher you need to start the time over. Once your fish are cured you need to very slowly (over a week or more) increase the salinity of the tank to match your display. You still need to keep your fish in the hospital tank for the full 72 days.
Copper treatment requires either cupramine or chelates copper like copperSafe. You also need a copper test kit compatible with the copper you choose. follow the instructions on the package. Chelated copper is easier to use.
Once your display is ready to get the fish back add them. Sterilize the hospital tank and all the equipment in it with 10% bleach. Make sure it is pure bleach, some have surfactants added and you don’t want that. It is usually the super cheap bleach. Let the equipment air dry completely (About 48 hours). Now the tank is ready to be set up as a quarantine tank. The set up is identical as for the hospital tank. This will be where you quarantine any new fish (one at a time) for 30 days. Some like to treat for inch and other parasites while the fish is in QT. Unless it is a tang or a rescue from ***** I just observe and treat if necessary.
Your 54 gal is a small tank You can’t do any tangs in it. They need space to swim even when they are very small. As they get older they get very territorial (all SW fish do this) and will be aggressive Especially in a small tank. In your 75 you could do ONE tang but only a bristle tooth like a Tomini, kole, or similar. Keep track of tank size requirements and adult size of these fish. Only buy what is appropriate for your tank or you will end up with a lot of aggression resulting in stressed fish that have health issues.
