Starting a New Aquarium: Fish Compatibility

When you start a new aquarium, there are two main factors to think about. The first thing to think about is how many and what size fish to start with for the container that you have. This first factor is important because putting too many fish together in one tank, or putting fish that are too large in a container that is too small, will cause great fish stress as well as lower the water quality.

The second factor is determining which fish get along well with which fish. This is important because if you have fish that are very incompatible in size and/or aggressiveness, the bigger and more aggressive fish may chase, harass, or even eat the other fish, causing great stress throughout the aquarium. What will stress do to fish? With enough stress, most fish will have weakened immune systems and become more vulnerable to fish diseases. In this article, we give you the information you need to help minimize fish incompatibility and stress.

What Fish To Start With For The Container You Have

As mentioned above, the size of the aquarium or other fish container is a major factor in determining which fish to start with or get. You must make sure not to overcrowd your aquarium. For any fish, the rule always holds: the bigger the container the better. Fish tanks are not expensive, and buying a nice, big tank is the best thing you can do for your fish. You should avoid keeping your fish in a goldfish bowl or other small container, no matter how hardy or small the fish is.

In general, for fish that grow up to 1 to 5 inches, you should have at least 1 to 5 gallons of aquarium water per fish. Some good fish to start with for this size include zebra danios, guppies, bettas, white clouds, platies, small tetras, small catfish, small swordtails, small gouramis, and fancy goldfish such as fantails. For keeping a few of these fish and other fish that will not get very large, a smaller aquarium such as a 10-gallon aquarium would be fine.

Keep note of fish that start out very small but that may grow much larger. Examples of these kinds of fish are angelfish and certain cichlids. A small, one-inch angelfish can grow to up to 6 inches long within a year, and up 10 inches from top to bottom. Because angelfish are such tall fish, they do best in larger tanks (at least a 20-gallon tank), especially if you are going to keep a couple of them. The ideal is to have at least 5 to 10 gallons of water per adult angelfish. For larger tanks, some other great choices include oscars, swordtails, mollies, large tetras, large gouramis, silver dollars, and large catfish.

Some fish must be kept in a very large aquarium or even a pond to thrive. Big, hardy, fast-moving varieties of goldfish, such as common goldfish and comets, will usually grow too big for an aquarium. These fish can grow up to around 12 inches long, and they are excellent choices for starting in a pond. If you must use an aquarium for fish that grow up to this size, the ideal is at least 20 gallons of water per fish. Koi, which can grow up to 3 feet long, would need to have about 500 gallons per fish and are pretty much only kept in ponds.

Do remember that after you set up your aquarium, you must wait for it to become established before adding any fish. Aquariums are considered established after 6 to 8 weeks, and "established" means that there are enough beneficial bacteria present to break down the toxins from the food and waste. After that, it is a good idea to start with just a few fish at a time, and add the hardier fish to the tank first, such as guppies, goldfish and catfish. It is also best to avoid the more sensitive (less hardy) fish, such as neons, mollies and angelfish, when you first set up an aquarium. Let it get established for a few more months, make a few partial water changes and then when your water looks really good, you can add some of these fish.

Which Fish Get Along With Each Other

To help ensure that most fish get along with each other well, the general rule to follow is to make sure that your fish are about the same size (with a few exceptions), about the level of aggressiveness and temperament, and about the same level of hardiness in terms of temperature and pH requirements.

Let us first talk a little about fish hardiness. Tropical fish are classified into tropical freshwater fish and tropical saltwater or marine fish. The vast majority of fish owners keep tropical freshwater fish and we will focus on these fish here. The most ideal temperature range for most tropical freshwater fish is 76 to 80 degrees, and the ideal pH is 6 to 8. As you can imagine, most tropical freshwater fish will do great together with each other in terms of common temperature and pH, all you would need to do is try to keep their sizes compatible and avoid keeping aggressive fish and timid fish together. Tropical saltwater fish are much less hardy and require much different conditions, and would not be kept with tropical freshwater fish.

Due to its peaceful temperament and appearance, the angelfish is one of the most compatible fish around, and is often put together successfully with smaller types of fish. The only times angelfish may get aggressive are when they are feeding or spawning. Even when being aggressive, angelfish only tend to be aggressive with each other. You can keep angelfish with many other kinds of tropical fish. Gouramis, swordtails, and larger tetras make very good tank mates for angelfish. The only major rule to follow is do not keep angelfish with fish that could fit into their mouths, as angelfish may try to eat the very small fish. These may include very small guppies and neons.

Though aggressive amongst themselves - especially the males, bettas can be kept in a community aquarium. Just make sure that you do not put a betta with other small, aggressive fish, such as tiger barbs, cichlids, or another male betta! The betta should be kept with the same size or larger fish, as they are known to attack or eat smaller fish such as very small guppies or neons. The larger fish should not be of a very aggressive temperament though, so that they do not try to attack or eat the betta. African cichlids might be too big and aggressive for a betta. Even with these rules, you can still put a betta with many other fish in a community aquarium. For example, you may put a male or a female betta with tetras, swordtails, mollies, platies, some of the tamer barbs, and some gouramis.

As mentioned earlier, big varieties of goldfish such as common goldfish and comets can grow up to around 12 inches, and are excellent for the pond. They are very compatible with koi in a pond in terms of size as well as temperament since both are very active and fast-moving. These goldfish and koi can also both be kept in water ranging from 35 to 80 degrees, and are therefore also compatible in terms of hardiness. Fancy goldfish such as fantails are round in shape, small, slow moving, timid, and less hardy. They should not be kept in a pond with the big, hardy varieties of goldfish above or koi. They would do great with other smaller tropical fish such as angelfish and guppies in an aquarium.

Finally, if you are a beginning fish hobbyist, it is probably best to be careful about keeping unusual fish like piranhas, blind cave tetra, and pufferfish. These fish will probably be hard to start with and difficult to keep with most other fish. For example, although the piranha is not as aggressive in a tank, you would not want to keep much fish other than piranhas together. As another example, the blind cave tetra would probably be easily picked on by most other fish. It is usually best to keep unusual fish by themselves.

If you have questions about how to start an aquarium or pond and fish compatibility, just ask us and we will help you any way we can.

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