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Home Aquariums

Keeping local fishes in home aquariums is becoming increasingly popular, in part because 1) our native and introduced fishes are just as interesting as pet store fish, 2) they are typically easy to catch and are free, and 3) many are hardier and easier to keep than common tropical fishes. There is arguably no better way to become intimately familiar with fishes than to observe them in aquariums. Closely observing fish form and behavior gives us a deeper appreciation of how exquisitely adapted they are to their watery worlds.

One of the best ways to learn about and appreciate fishes is to observe them in a home aquarium.

Before continuing, you must realize that once you have taken your fish home, you should plan on keeping it for its life span. In almost all states it is illegal to release fish into waters other than where taken. In Connecticut, it is illegal to transport a fish for the purpose of releasing it (without a liberation permit), even if you are planning on putting it back where it came from. The reason for these laws is to protect the integrity of lake ecosystems from introductions of new species. Introductions of aquatic nuisance species is a big concern nationwide. By moving fish from one water body to another, you can inadvertently introduce new diseases or nuisance plants (the seeds of which may be in the water with your fish). Also, fish are genetically programmed to best survive in the waters of their birth. If moved to another water body, they may have trouble competing with local fishes or could compromise their gene pool by interbreeding with them.

A couple of reasons that local fishes are easy to keep in aquariums are that they do not require a heater (as do tropical fish) and are often very tolerant of less-than-perfect water quality. There are a number of excellent references, both in book form and on the Internet, on keeping local fishes in home aquariums. 

Presented below is just an overview. Details on specific fish are presented in later sections under the fish family descriptions and in the “Habits” sections of individual species.

Equipment and Supplies

A moderate investment in aquarium supplies is necessary to get started. Your local pet store owner will be more than happy to help you select whatever suits your need and price range. Below is a list of basic equipment and supplies needed to start a home aquarium for local fishes.

Aquarium. You can keep a few small fish in a 10-gallon aquarium. These “starter” aquariums are cheap, but many local fishes grow fairly large, so a larger aquarium is more versatile (also more expensive). A rule of thumb that is pretty close for most of our freshwater fish is “an inch a gallon,” meaning you can easily keep fish totaling about 10 inches in a 10-gallon aquarium (for example, five fish that are two inches long or two fish that are five inches long). More than that and the fish start to get overcrowded and stressed.

Cover and Light. Your aquarium needs a cover to keep fish from jumping out, and a light to help see them better.

Gravel. You will need one-half to one pound of gravel per gallon capacity of the aquarium. The gravel serves as a place to catch waste and as a substrate for bacteria to grow on. Just like in the wild, bacteria that grow on the gravel will break down fish waste products, helping to naturally clean your tank. You can use natural stream gravel if you clean it well and sort and discard the smaller and larger particles (most aquarium gravel is 3/8 to 1/2 inch in diameter). It is probably easier just to buy gravel from your pet store.

Filter. Filters trap excess food and larger particles from the tank water and, more important, house a lush growth of bacteria to break down organic waste. They also incorporate ammonia-removing substances and carbon. In a very small tank, you may be able to get away with one of those small filters that use pumped air to circulate water. Local fishes tend to be large and produce a lot of waste, so an external filter (which has its own electric pump) is the best idea, regardless of tank size. Make sure to buy extra filter cartridges and carbon, which are disposable and should be changed regularly.

Air Pump and Accessories. In nature, oxygen is constantly being added to water through contact with the air and as a byproduct of photosynthesis by aquatic plants. In your aquarium, an air pump with plastic hosing and air stone are necessary to adequately replenish oxygen used by the fish.

Other Recommended Accessories (sold at aquarium shops).

  • Small dip net for moving fish.
  • Under-gravel filter to supplement the external filter.
  • Sponge for cleaning algae off inside of aquarium glass.
  • Gravel vacuum/siphon hose for cleaning gravel and siphoning off water.
Rocks and Plants 

Your fish will be generally happier and your aquarium more attractive if you provide places to hide behind plants, rocks and other structure. Many of the larger native fishes will uproot live vegetation, so plastic plants bought from the aquarium store work just fine. Flat rocks leaned up against the side of the aquarium provide shelter from other fish, but still allow you to see behind them. 

Water

Well water can usually be added directly to an aquarium. Treated (municipal) water should be allowed to sit for at least two days to allow any chlorine to escape. One conservative way to ensure that your water chemistry is suitable for your fish is to use as much water as possible from where the fish was captured. When setting up a new aquarium, run the air pump and filter for a few days before introducing any fish to the tank. Keep in mind that estuarine and marine fishes are logistically more difficult to keep because they need at least some salt content in the water, which must be regularly monitored with a salinometer.

Balancing Your Fish Community

In the wild, fish compete for food and space, and it will be no different in your aquarium. Some fish species (such as most minnows) are passive and relatively fragile, while others (such as most sunfish species) are tough and territorially aggressive. The passive fishes typically do not bother each other or any other species, while aggressive species may chase, harass and eventually kill their competitors (or eat them if the size difference is great enough). Juvenile fish are typically not as aggressive as adults.  Passive fishes do best in the absence of aggressive species. However, you can experiment with mixing the two types by stocking your tank with larger passive species and smaller aggressive species. Of course, expect your fish to grow, causing the balance to eventually change.

Fish Food

Many of our local fish species can be acclimated to accept dried fish food, such as flakes and pellets. However, most native North American fishes are carnivorous, typically eating insects, crustaceans and/or other fish in the wild. For this reason, it is best to supplement the diet of most species with at least some live or fresh-frozen food. Some of the more predatory fish species (such as those of the pike family) will eat only live food and are logistically more difficult to keep for this reason. Larger aquarium stores sell just about everything you need to satisfy any species’ diet. For “easy” fish species, such as an assemblage of sunfish, minnows and catfish, all you need to keep them happy is to purchase some floating flakes and sinking pellets (make sure they are for carnivorous fishes). To supplement this diet, occasionally offer them earthworms or nightcrawlers cut into small pieces. For estuarine and marine fishes, try freeze-dried krill, shrimp and/or worms, supplemented with frozen squid. When you first put wild fish into an aquarium, they must learn to eat prepared food. It is usually best to start them off with natural food, such as cut-up earthworms, and introduce them to dried food once they have gotten used to living and feeding in your aquarium. Juveniles of most fish species are quicker to accept dried food than older fish. If you are ambitious enough to keep fish that require live food, you can purchase “feeder” fish at your local aquarium shop. Seasonally, you can try to catch your own small fish with a dip net or seine to feed to your larger aquarium fish. Feed your fish daily, or at least every other day, but it is important not to overfeed them. Overfeeding results in reduced life span, fish quickly outgrowing the aquarium, and fouling of tank water.

Keeping the Water Clean

Unless you keep only a few fish in your tank, things will get messy after a while. Also, keep in mind that fish are forced to live in their own toilet, so keeping the water clean is important to their health. Your filtration system will do most of this work, but make sure you change the filter cartridges often (do not let them get completely clogged). Occasionally use a vacuum/siphon hose  to clean the gravel. Changing 20 to 50 percent of the water every two to four weeks will keep it in good condition. It is not a good idea to regularly empty the tank and completely wash the gravel, because drastic changes in water chemistry will stress your fish and you will lose the beneficial microorganisms in the gravel that process fish waste products.

Text and images adapted from Jacobs, R. P., O'Donnell, E. B., and Connecticut DEEP. (2009). A Pictorial Guide to Freshwater Fishes of Connecticut. Hartford, CT. Available for purchase at the DEEP Store.