My marine fish died from ich. How do I prepare the tank for new fish?

If the infection is cleared, wait a couple weeks and then consider repopulating the tank. Ideally, you should set up a quarantine tank for incoming fish before they go into the main tank. Monitor them for a week or two to confirm good health. You may even want to administer an antiparasitic medication while in quarantine to be safe.

Ideally, the tank should be kept at about 86 F for two weeks to resolve Ich infection. The gravel or substrate should be vacuumed and tank furniture sanitized. If you are setting up the tank anew, you will have to allow time for it to properly cycle prior to adding fish.

When there is an ich infection, it is necessary to treat the entire tank, even the fish that are not symptomatic. Ich has 3 distinct stages in the life cycle. Tomites, the free swimming stage, are most vulnerable to treatment. Once on the fish or encapsulated in the substrate, ich is very difficult to treat. A combination of increased water temp, aquarium salt and commercial medication can be used to treat ich. The increased water temp, 86F, will significantly speed up the lifecycle. It can take 1-2 weeks to treat minor infections and longer for more severe infections.

Increase the temp, gradually, to 86 F and hold it there for at least two weeks. This will speed up the ich lifecycle. When the parasite is free swimming is when it is most susceptible to treatment. Once the spots drop off your fish, perform a major water change and vacuum the substrate thoroughly. If you have live plants, remove them and gently wipe them down, if you have artificial plants, remove them and sanitize them. The same goes for any tank furniture. Use the ich medication according to label directions. Keep the water temp elevated for 3-5 days after treatment and after all symptoms have resolved. Gradually reduce water temp back to normal afterwards. There is no definitive way to determine if the infection is resolved. You will to monitor the fish closely and repeat the process if necessary.

If left untreated, ich will eventually kill. It can weaken the fish after which infection will set in and finish it off. It is also possible the fish were killed if a water change was done as part of the cleaning. Aged or conditioned water should always be used to avoid exposing fish to harmful chemicals, mainly chloramines, many municipalities use in treatment. Water that is not temperature matched can cause shock which will also kill fish. If can be treated by gradually raising the water temperature over 24 hours to about 85 F. Ich is temperature sensitive, this the warm water will speed up the life cycle. Once the "dots" fall off your fish, vacuum the substrate and then use a commercial ich treatment. Leave the temp at 85 F for 2-3 weeks to clear the tank. Afterwards, gradually decrease temperature to the proper temperature for your species of fish.

The safest treatment would be a temporary increase in water temperature and some plain aquarium salt (NOT table salt). Ich is very sensitive to temperature. Gradually increase water temperature, by no more than 1 degree F per hour, up to 86 F. Hold it at that temperature for at least 2weeks. This will speed up the life cycle and prevent reproduction. You can perform partial water changes (30%) and vacuum the substrate during treatment. Use only aged or conditioned water that is temperature matched to prevent stress or shock. An airstone should be used to increase oxygenation since warm water does not hold as much oxygen as cooler water. This could affect some the fish. Aquarium salt can be dissolved into the tank at 1-2 teaspoons per gallon of water. Dissolve it in a cup of tank water then pour it gently into the tank. When performing water changes, treat only the amount of water being replaced with salt, not the entire tank volume. After 2 weeks, gradually decrease water temperature back down to species appropriate levels.

Gradually increase the water temp to about 80 F. This will speed up the lifecycle of the parasite. Once all the spots have dropped off the fish, you can use a commercial ich treatment. Look for one in the aquarium section of the local Petco. Follow label directions carefully. If you have just a few fish in the tank, you can remove them to a separate tank after the spots have dropped off. Leave the main tank empty for 4 days at 80 F. The ich parasite cannot survive without fish, so they will die. After 4 days, perform a partial water change, vacuum the substrate, wipe down tank furniture and return the water temp to normal. Acclimate the fish to water temp before returning them to the water.