What Fish NOT To Get: How To Know

Posted by on November 14, 2013 - one

For starters, This is no home for a tang!!!

World’s Smallest Reef Tank


Are you considering a stocking list for your aquarium? Probably not. If you are like most hobbyists you wish for fish but buy what you have available during that spontaneous moment, often leading to a future of regret and endless nights trying to capture your mistake. If you have not been in that situation than you are one of the few who do actually plan! We can’t all spend hours researching and not everyone has access to a reliable saltwater expert that isn’t just trying to sell something. There are a few things to rule out over all other reasons NOT to get that fish.

Here are some issues other people have had with spontaneous purchases:

Annoying things your livestock does and stupid mistakes.

Size Matters

How large does the fish at hand grow to? Most hobbyists have between 10-200 gallon tanks, which seem like a good amount of space, but are actually considered small in the world of marine fish. After all the ocean is HUGE!!! Some fish reach 3 feet long and are predatory…Groupers, sharks, rays…Oh boy! Stay away from them as much as you want, they are not good fish. You need a gigantic tank to even consider raising these fish for their naturally intended lifespan, not to mention the cost to feed a tank of full grown sharks! There are huge tangs and angel fish that often die without warning when their body realizes they are in too small of a tank. This often causes immune systems to shut down and if you have ich in your tank it can easily over power the fish during the weak state. Keep your fish list down to reasonable sizes and leave room for extra fish because after 2 years of the same 12 fish you will probably add another one just because…we all want more fish! The smaller the fish you pick the more you can have! Make sure not to overstock your tank either, as this can also cause aggression. Here are some experiences with fish numbers.


Damsels define aggression. They are mostly quite nippy, and VERY territorial! They are very cheap and quite abundant, only because they are so mean!

Are you planning a tank for fish or “a” fish? Not a lot of people like setting up tanks just for one fish. If you plan on having a community tank, or a tank with predators, make sure they are not the kind of fish who just snap at a certain stage in their life. Never house a predator with its prey unless you intend to use this animal as food. This prevents a lot of issues down the road when you are trying to re-home a full grown lunar wrasse who eats every fish he can find. If you are the kind who gets bored with the same fish, try to at least keep the lineup something that will be easy to re-home or trade. It is much easier to sell a clown fish than it is to sell a ray. Also keep in mind aggressive inverts such as mantis shrimp!

mantis shrimp image via realmonstrosities.com

mantis shrimp image via realmonstrosities.com

Most of the time you cannot put the same species together. Usually similar looking fish do not work well either. Some wrasse resemble hawk fish, and that generally results in a fight. Sometimes this works, but not that often. Besides, a variety looks cool anyways! A tank with 59 Picasso Clownfish may seem cool at first but after a while it tends to get a little too funny.

image via reef2reef member marvinsreef

image via reef2reef member marvinsreef

Some fish are born to be mean. There is no stopping mother nature when she is in the form of a full sized trigger fish gnawing at your wrasse. A damsel will not be nice to nice fish, as pretty as they can be. Since even pretty fish can be extremely aggressive you must avoid sporadic purchases. If you see a fish you may want and are worried someone else may buy it put it on layaway or buy it outright and have them hold it for you while you study. If it turns out that fish won’t work for you just transfer the credit to a better fish! If they don’t let you do that then they aren’t worth your money!


Some fish are just plain stubborn! It is not their fault, as we took them from the sea where they had living food at all times. Some fish will just not accept any food in captivity. Wild caught fish are especially harder to food acclimate and when you can find the Captive or Tank raised versions you should always get them first. Make sure to avoid specialized diets. Berghia Nudibranch only eats aiptasia. NOTHING ELSE!!! if you do not have a tank full of them they will starve very quickly. Make sure you check into what these fish or animals eat and watch them be fed if at all possible to avoid buying a stubborn fish.

Some species are only available in the sea. Either nobody has had luck breeding them, or haven’t tried. Not all fish from the sea are bad for the aquarium, most of the risk is the diseases that come with them. The ocean has so many types of problems that could at first be unseen to the divers that could contaminate your tank.

Delicate Fish

Next we have the delicate fish. These include fish with specialized diets. Fish and animals that only eat one thing are usually found near abundance of that particular food source, which is hard to achieve in the standard reef tank. Other fish just require beyond extreme stability and water quality and will die under the finest of circumstances without warning. I have seen quite a few butterfly fish die when acclimated because the persons water was not pristine.

Moorish Idol requires a specialized diet and has a high mortality rate in the home aquarium

Moorish Idol requires a specialized diet and has a high mortality rate in the home aquarium

Most Fish Supply websites specify the animals origins and even give you options. Some LFS (local fish stores) do, but not all. Of course some LFS sell coral but cannot tell you if it is an LPS, or NPS. Avoid these places if at all possible, your money just encourages them to keep slacking. Sometimes an hour and a half drive is worth that perfect fish.

With the right idea to begin to narrow your list you can start to research the fish on your mind. Remember, RESEARCH NOW BUY LATER. There are plenty of fish in the sea. Your aquarium can potentially stay running for 10-50+ years if you play your cards right, and if you pick your fish right they will live with you for a good chunk of that time. Fish will die of old age, luckily corals live forever until they are killed!

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