Wow, where to begin....
Let me first begin by saying that some of this information is confusing because of how it is presented. I am concerned because there are many inexperienced hobbyists who will be reading this thread, and they may be presented with many issues and even fear of keeping a marine tank due to misinterpretation of what has been written here.
The first thing I would like to point out and go back to is the issues of compression/decompression. For starters, the number of aquarium fishes (saltwater or freshwater) that go through decompression upon collection is very few. Yes, our store has worked with trans shippers, and I am very familiar with the the procedures and issues. (our favorite to work with was Pacific Island Imports)
The swim bladder issues that were mentioned in connection with compression/decompression is what has me so thrown off here. What is being described with the swim bladder issues & sinking to the bottom is not a compression problem, but instead is what we refer to as pH shock...
In mentioning the physiological functions of the fish I would like to explain pH shock and what actually happens inside the fish. When a fish has been in a bag for such an extended length of time, waste accumulates in the water (the smaller the amount of water in the bag the higher the waste concentration), which over that time drops the pH of the water inside the bag. When that fish arrives at the wholesaler, lfs, or etc. the tank that the fish will be moved to has a drastically different pH than the water contained in the bag. (We have tracked pH in the bag water over the yrs, and some of those levels drop as low as 7.0 due to the length of time the fish has been in that bag) There are many different acclimation procedures used by different lfs's. When acclimation is done improperly there is a rapid shif in pH which affects the nervous system of the fish, and in many cases, impedes the fish's ability to absorb O2 through the gills. It also can impede the nervous system's ability to regulate gas exchange in and out of the swim bladder by way of circulatory system (blood stream). If there is not enough gas in the swim bladder and the fish cannot add more to it, this causes the fish to sink... which is all regulated by the nervous system. If there is too much gas in the swim bladder and the fish is not able to diffuse it out through the blood system, this can cause the fish to float. Stress is also a large factor in this physiological process. The key is to make the acclimation of the fish as least stressful as possible by making sure the pH of the water is close enough, salinity is close enough, and temps are close enough to the tank water.
While I can't deny that in some fish the compression/decompression may be an issue, I also have to then recognize that those issues are primarily something the collectors are dealing with, and as said, in very few species. The differences between 1 inch, 12 inches, 36 inches, or even 5 feet of water for these animals is not going to be what causes the rapid change in your success rates. It is also important to recognize that if the collectors are having issues with compression/decompression in the animals they collect, they would have no business. Wholesalers and retailers are not going to do business with anyone who has such a high death rate in their animals because that causes loss of business & money for wholesalers and retailers alike.
What IS going to be the difference in your success rates is the proper acclimation when it comes to water chemistry, salinity, stress, temp fluctuations, etc. which we have described in depth here already.
The mention of the need for a dark room and lack of people during acclimation is also something that is not practical for a wholesaler, retailer, etc... nor is the ability to quarantine these animals for weeks at a time before offering them for sale.
In the retail industry, each day those fish are in the store tanks it costs the store money. The list of expenses is long... food, water, salt, electricity, medications, and the manual labor required to care for these animals all costs money, not to mention the amount of tank space these animals would require. While spending all of that money the store is not making any money, thus the retail cost of these animals would have to greatly differ. A $10 fish would suddenly cost $100 to make up for the extra costs involved in the lenghty quarantine. It is for this reason that hobbyists should have a quarantine tank on hand at home, and any new fish should first spend 2 - 3 weeks in quarantine before adding it to the main tank.
One other point that deserves recognition here is that many saltwater fish, because they are still being wild caught, do come to the retail industry with various illnesses and parasites, and not all of these illnesses and parasites can be properly identified (or even noticed at all) within the first couple of weeks the fish is in a lfs tank. Some illnesses and parasites are masked by the stress factors involved in shipping and retail tanks, some of them simply don't manifest obvious signs until in an advanced stage. This is another reason why all hobbyists should maintain a quarantine system at home.
In reference to the slime coat and netting the fish... I have to say that it would take awful rough handling to actually remove the slime coat from a fish. A fish's body produces slime coat naturally as protection against illness, disease, parasites, and stress. When in a stressful situation the fish will shed some of this slime coat, but the body is continuously producing more. Some fish have heavier slime coating than others, and some fish will expel more than others depending on their circumstances & species. The importance in moving a fish is not as much based on net vs cup as it is to the amount of stress the fish experiences during capture. If a fish is being chased endlessly it is going to suffer severe stress, be it a cup or a net situation... which will result in the loss of some of the slime coating, among other things. The problems of cloudy eyes are seldom due to being handled in a net, but are most often caused by illness and parasite issues. One of the most common is flukes & protozoans.
While I wholeheartedly agree to many things that have been said in the course of this thread, such as the issues of proper acclimation in all fish, saltwater and freshwater... there are other parts of this thread that made no practical sense to me due to the way it was presented. I hope I was able to clarify some things with this post and able to reassure those who read this thread that it is many factors that are responsible for the high death rates in our aquarium fishes, but most of those issues are easily resolved with proper acclimation and quarantine procedures.
Our death rate here in fish here is very low because we take all of these things into account and take appropriate steps to make the transistion our animals go through as easy as is possible. We have many methods of acclimation we use, and it varies depending on time availability, species of animals, the way the animals were packed and shipped, where they are coming from, time of year/weather, and various other things.
One thing I would like to say in finishing is that the clownfish in question by the author of this thread is not suffering from issues relating to this content as far as we can tell. With the information that was provided, it sounds as if this fish suffered neurological damage somehow, and for that, there is no cure, no treatment, no recourse of any kind that would be of any help to the fish. While that is a sad thing, it is fact that sometimes these things happen and are out of our control, and it doesn't mean there was mishandling of any kind involved.
I apologize for the length of my post but there was alot of material to cover here. I would strongly suggest that if this discussion of acclimation, compression/decompression, etc continues, it should be done in a thread of its own so as not to hijack someone else's thread.