fish scratching themselves

Question
I have a marine aquarium.  all my fish are scratching them selves.  It just started of the past couple of days.  I added two new fish but I have also been supplementing allot.  The store suggested using melafix marine.  I really don't think its an infection because none of them have any visible scars or anything (except one).  I am thinking it is a supplement that may be bugging them or something brought in from one of the new fish.  I have a clownfish, Pigmy angel and Twin spot goby,  I added a dwarf flame and midas blenny.  The dwarf flame was itching from the minute he entered my tank and now the blenny and clownfish too are this morning.  The pigmy is just darting all over the place.  The goby does have a hole on his bottom fin that started two days ago.  I cant tell if it is from a scrape or what.  I would like to do a water change first see if that fixes everyone and treat the goby separate.  what do you think?  by the way the supplementation has been to get my polyps (zoads) to open up.  They all closed up after my last water change which oddly kicked off a cycle in my tank and I have been trying to get it under control ever since.  Prior to that everything was perfect. I add algea control (almost fixed), calcium, tech 1, amino acids, vit c, buffer, prime, and phyto plankton.

Answer
Hi Monica,

While an Ectoparasite infestation is the most common cause of this behavior, the scratching could be something else. Fish can be irritated by metals such as mercury, iron, and copper in the water, and often times these can be introduced when using non filtered tap water for water changes, or when combining, miss-dosing / over-dosing liquid aquarium additives & supplements.

If this is the cause, the fish seem to "scratch" most often right after a water change and less as they get used to the irritant. Then the cycle can be repeated at each water change, if continuing to use non-filtered tap water of if continuing to miss-dose / over dose certain aquarium additives & supplements. Note that these reactions are not the same for all fish all the time.

Fish can also scratch in response to parasites, including other the more obvious Ichthyophthirius (ich).

Elevated levels of ammonia, nitrite or high/low/widely fluctuating shifts in pH can also trigger irritations.

Tips:

-- Use reverse osmosis water during water changes.

-- After each water change, add a small dose of good beneficial bacteria like Brightwell Aquatics MicroBacter 7. See this link showing this product if you are not familiar with it. http://www.ocreef.com/brightwell_aquatics_microbacter7

-- If you are not utilizing a good protein skimmer as part of your overall water filtering, than I would highly recommend to start using one.

-- Cut back on adding all of the various water additives and supplements that you are using. The main parameters to worry about when maintaining a healthy saltwater coral reef / fish aquarium, include: pH, salinity, calcium, temperature, redox, "doc" dissolved organic compound levels, lighting, and feeding regimens.

-- When possible treat an infected fish in a separate tank, you never want to treat your whole tank if you can avoid doing so. If you need to treat for ich there are medications that you can use with success such as formalin. Closely follow all manufactures instructions.  

-- Last but most important, all new fish should be quarantined for 30 days prior to being added to your main show tank.

I wish you a speedy recovery with your aquarium.

Sincerely,
David