Fish are dying

Question
I have had a 90 gallon salt water tank for 3 years.  I have two crabs who are fine and one of my original damsels from when I cycled the tank.  When I buy new fish they are fine for a few weeks and then they will all die within 24 hours of each other.  I did see white dots on a tang this last "round" of fish I bought.  I suspect it is ich but don't know why the damsel would not be affected.  Should I assume it is ich going through its normal life cycle and it is being sustained by the damsel and therefore treat for ich?  

Answer
Hi Patrick,

It does sound like the Tang has marine ich.

When treating your fish, remove them from your resident tank and treat them in a separate pre set-up aquarium. These aquariums are called sick tanks or hospital tanks. The aquarium doesn't need to be an elaborate set up, it can be a simple, small five gallon aquarium. An aquarium that makes both a good hospital tank, and a good quarantine tank, is the Marineland Eclipse aquarium. This aquarium is great for this purpose because of its size, and because it's an all-in-one unit, including filter and lighting. To quickly fill it, go to your nearest Petco and get their 5 gallon ocean water. This will quickly give you an instant hospital tank/quarantine tank. See the link below for a reference of these two products.

http://www.ocreef.com/marineland_eclipse_explorer_ii_aquarium_kit?category_id=49...

http://www.petco.com/product/11884/PETCO-Real-Ocean-Water.aspx

The original damsel is less likely to contract a disease because it is use to the aquarium that it resides in, and therefore doesn't get exposed to the stress that the new fish get exposed to when being introduced to your aquarium for the first time.

Fish typically get sick when being introduced to an aquarium because they are stressed and their immune system isn't working at full capacity, therefore they are more likely to contract an illness.

My recommendation for adding fish in the future is to put them in a quarantine tank first for a least a couple of weeks, before introducing them to your resident tank, so you can monitor them and treat them accordingly if needed. My recommendation for any existing sick fish that you may have, is to treat them in a hospital tank and not your main show tank/resident tank.

Regards,
Dave

All Experts -Editor