A lot of time is spent on the threads discussing the proper setup of a marine aquarium, and how to maintain the aquarium. Oddly enough, it seems that we almost never discuss what I would consider to be one of the most important aspects of having a successful marine aquarium, which is proper fish selection. With this article I want to discuss how to select healthy fish, as well as touch on a few other important aspects of fish selection.
First things first, it always pays to create a stocking list up front. Knowing what fish you plan to purchase will help you in deciding which order the fish should be added. Different fish will exhibit different behaviors after they become settled into a tank, and the order in which you add fish is a very important part of ensuring that your fish will mix well together in a given aquarium. For example, if you want to keep both a Yellow Tang and a Kohl Tang together in a 125 gallon tank. This combination is certainly possible, but will have a much higher chance of success if you first purchase the Kohl Tang, and then add the Yellow Tang at a later time. These small decisions are very important in a marine aquarium, and need to be taken seriously.
As you create your fish list you should consider both the needs of the fish and your experience level in keeping marine livestock. A lot of fish are suitable for an experienced marine hobbyist, but would be very difficult for someone with a beginner level of knowledge to properly care for. In these situations, there is no level of book knowledge that will help you gain this experience. Experience is something you gain with time and hands on fishkeeping.
For example, regardless of how many books you read on flying an airplane, I am pretty sure you would want a co-pilot the first time you take the air! A pilot needs so many hours of flight time, hands on experience, and so do you are a marine fishkeeper. You need to accept this up front, or you will make mistakes that are preventable. I frequently see fish in the hands of a beginner that would be excellent fish for someone with a few years experience. Some examples are the BiColor Angel, Lemon Peel Angel, Racon Butterfly, Pearscale Butterfly, Powder Blue Tang, and Mandarin Goby. These fish show up frequently in the trade and almost always cause problems for a new marine fishkeeper. There are many examples of these fish, so be sure to ask around on the forums BEFORE you make a purchase. Selecting fish which fit your level of experience will greatly improve your odds of having an enjoyable experience in the saltwater hobby.
Once you determine that a fish is suitable for your experience level, you need to decide if your aquarium is the correct environment for the fish. It is a huge mistake to purchase a fish on the assumption that you will upgrade to a larger tank in the future. You need to purchase fish which are capable of living in your aquarium at their adult size! Reef fish grow very rapidly, far faster than what you are accustomed to in a freshwater tank, and you need to allow proper room for growth and development. As a general rule, you will find two types of fish in the trade. There are fish that hang out within the reef structure most of their day, and there are fish that swim in the open water, covering large territories. As a general rule, these open water fish, such as Tangs, Rabbitfish, and large Angelfish, need a minimum of a 6 foot tank length. If your tank is less than 6 foot in length, then you need to create a stocking list of fish that are suitable for such a tank. This would include dwarf Centropyge Angelfish, Clownfish, Gobies, Blennies, and most other fish with an adult size of under 5''.
Now that you have determined the fish you wish to keep, it is time to go shopping! At this point your research should be done, and you should have some very good ideas of exactly what fish you are looking for. You will probably have 2 or 3 fish that can be added in any given order, and then a couple other fish that need to be added last. As a final though before your first purchase, it is vital that you have a seasoned quarantine tank (Q tank) ready for your fish when you bring it home. It is useless to do research and carefully select fish at the LFS if you do not have a Q tank to isolate all newly purchased fish. Fish need time to adjust to life in captivity and to rebuild their immunity system, and you need time to observe the fish for disease which can take weeks to present themselves to the naked eye.
Selecting a healthy fish at the LFS also takes a trained eye, so you will want to spend some time just observing fish. I strongly suggest never buying a fish on the first visit. I usually visit 2 or 3 LFS in a given day, making mental notes of possible fish purchases. I note when the fish arrived at the LFS, and the current physical condition of the fish. I will generally try to visit the fish again within a few days, and if the fish still looks healthy I will ask the LFS to hold the fish for a few days longer. If an LFS is unwilling to hold a fish, then they do not deserve your business. All LFS experienced and reputable in the marine business will hold a fish for a few days prior to your purchase. If they make this commitment to you, then you need to make the commitment to them and follow up on your decision to purchase the fish, assuming the fish is still healthy. Trust me, the last thing you want is a reputation with your LFS that you do not follow up on your commitments. There are plenty of customers out there, and believe it or not, the LFS will cater to its best customers. Wouldn't you?
Backing up a step, when you observe a fish at the LFS there are several things to watch for. First, is the fish swimming normally? If the fish is flashing or scratching at the bottom of the tank or at the decorations, the is a bad sign. Also, if the fish is swimming directly into the water currently, or quickly up and down up and down up and down, this is also a bad sign. Stay away from these fish. At best, visit them again in a few days to see if the behavior has changed. If you do decide to consider one of these fish for purchase, you should be very cautious and wait several weeks before buying the fish.
You also want to observe how the fish interacts with the other fish, or with the customers. Stand back a few feet from the tanks and watch the fish. Is it bold and swimming around, showing curiosity towards you and other fish? Or is it shy and just hanging or laying in one spot. Healthy fish will be active, and will engage their environment. They will often swim around pecking at the bottom of the tank or at the rock, scavenging for foods. These are good signs and something you should see before purchasing a fish.
Another obvious thing to watch for is visible damage to the fish. Are the fins frayed? Are there any red spots, swollen spots, or discoloration on the body of the fish? Are the eyes clear or cloudy? Do you see any white spots on the fins, body, or gills? Another body part to watch is the lips. Many fish will arrive with damage to the lips area. This is very common for Centropyge Angelfish, and almost always leads to infection and/or starvation. Look closely at the stomach. If you see a pinched or sunken stomach, this is a bad sign. If you see any of these symptoms, avoid this fish.
The next step is to identify what type of system the LFS is running. Are the tanks connected to one another? If so, are there sign of ich in any of the connected tanks. If so, avoid the system completely and move on. There are some systems at the LFS here locally that I refuse to buy fish from, regardless of how healthy the individual fish may appear. Remember, it can take many days to weeks for a fish to show signs of parasites, and you are almost assured that a fish in an infected body of water is also going to be infected.
If the fish you are looking for has passed all these tests, then it is time to get an LFS employee and begin asking questions. When did the fish arrive? I recommend allowing a fish at least 7 to 10 days to settle in at the LFS before taking it home. Again, visit in a few days and then ask the fish to be held for purchase. How did it adjust? Some fish do not adjust well, and you will be amazed at what the LFS employee will share with you, simply because you asked. Is it eating? If yes, ask to see it eat. Observe from a distance. An eagerly eating fish will aggressively go after food. If the fish is shy to feed, wait a few days before purchase.
As you are starting to see, probably 75 to 80% of the fish options are the LFS are going to be eliminated from consideration. Some days you will not find a single fish at the LFS that is worth purchasing, much less a fish that is one your list.
As a final note, NEVER make a spontaneous purchase. If you see a new fish that you did not have on your list, then ask questions here! This is why the forum exists, to help you make these decisions. Remember, on the forum we only have your best interest in mind. We are not trying to make a sale, and have nothing to gain.
Hopefully you found this helpful. As always, if you have questions, ask on the threads!