DIY Hospital Quarantine for Saltwater Reef Aquarium

What you need:

One air pump.
One ten gallon tank, clean and empty. (Ten gallons is a minimum, bigger is better!)
One 50 watt submersible heater.
One sponge filter suitable for a 55 gallon tank kept in the canister filter or hang on the back filter of one of your up and running tanks.
Spare saltwater kept circulated and heated.
Several small segments of PVC pipe for fish to hide in.

To set up:

Remove enough water from the tank the fish lives in to fill the hospital tank. If it's a new fish (from the store) be sure you drip acclimate it before plunking it into the hospital tank/QT.

Turn on (plug in and set to home tank temperature) the submersible heater in the 10 gallon tank.

Plop in the PVC pipe (optional in an emergency but helps prevent the fish from getting scared and stressing out) for hidey holes.

Remove the sponge filter from your canister or hang on the tank filter, attach it to the air pump, place it in the hospital tank, and turn on the pump.

Allow the tank to reach the temperature of the fish's home aquarium.

Transfer the fish into the hospital tank as gently as possible.

Change water out of the HT/QT tank every day to keep the water clean - even though you have a filter it isn't really up to the intensity of overstocking most Hospital Tank situations produce.

If the fish aren't sick to begin with and are just being QT'd don't medicate them. Medicating a healthy fish is a bit like giving a healthy person radiation and chemotherapy - it hurts the immune system. Just feed the fish high quality frozen foods soaked in vitamins and a HUFA (Highly Unsaturated Fatty Acid) supplement such as Selcon or Zoecon.

If your fish look healthy for 4 straight weeks, it's home sweet home for them. Don't forget to acclimate them to the destination tank!

If your fish are sick, please investigate possible illnesses or dietary deficiencies that may be affecting them and treat with the appropriate medications, dietary supplements, or hyposalinity treatments. Don't be shy about posting on reefing specialty forums for help with diagnosis and treatment of fish diseases but please do a search to see if your particular problem has already been addressed on the forum. Many internet forums are available to reefers and they provide a wealth of information and put you in touch with experienced reefers and even professionals.