HELP WATER PARAMETERS

[SoLiD]

If you're registering Nitrites that means that you have or had an Ammonia spike. I don't see that in your list of tests.

Test For Ammonia ASAP!!!

Ammonia is absolutely the Worse Substance you can have in any aquarium. It kills corals and fish alike. The ammonia could be from the mandarin decomposition or some other die off. Water changes are always helpful in any emergency. I'd do at least 2-3 20% water changes for the next couple of days to get your Ammonia and Nitrite levels down. Also how long has your tank been up (is it fully cycled), and what kind of biological filtration do you have in there (IE. live rock, deep sand bed, refugium). Your biological filtration is you best friend right now. It will convert the Ammonia and Nitrite to Nitrate and Nitrogen Gas (The bubbles in your sand bed) which aren't Toxic (with levels in reason) to your tank's inhabitants.

Activated Carbon wouldn't be a bad idea, but it doesn't bind to ammonia very easily. It will remove the iodine in your saltwater pretty easily though, so remember to check those levels too if you plan on using it. But maybe water changes will replace all the iodine being sucked out.

In closing, do multiple water changes, and make sure you have enough Biological Filtration. If you don't, get some in the near future.

Good Luck

-David