So how many fish can I add to my tank?
Before adding fish to your tank, you MUST safely cycle it. Please see "Cycling a Tank" for information on safely cycling.
Of co urse, everyone wants to put as many fish as possible into a fish tank. It's human nature, get the bang for your buck. You want fish out in the open so you can observe and see them anytime you want. Of course, this isn't the humane or responsible thing to do. Too many fish in a tank = too much waste, not enough swimming room, aggression, and ultimately, fish deaths. So how much is too much?
The cardinal rule for fish stocking is the "Inch Per Gallon" rule. This states that for every gallon of water in your tank, you can safely stock an inch of fish. When following this rule, you must calculate the adult size of the fish, head to tail. To figure out the adult size of a fish, please do your own independent research (the internet is a great resource!) as many fish stores do not provide accurate information. For example, if you have a 10 gallon fish tank (fully cycled of course), you could theoretically stock 10 inches of fish. This tank could safely hold and sustain 4 Harlequin Rasboras (1" each = 4 inches), 3 small platies (ONE sex, 2" each = 6 inches), a mystery snail, and maybe some ghost shrimp. For a total of 7 fish (4 inches of rasbora and 6 inches of platy = 10 total inches of fish in a ten gallon tank), you can see why a bigger tank is better, you can do much more interesting stocking.
Schooling fish: Many species of tetras, barbs, rainbows, and many others enjoy and need schools to be truly happy. Fish need schools for security. A single schooling fish alone in a tank will be scared, probably not be very visible, and will most likely never reach its full color potential. Some species of fish should be in schools to minimize aggression. Two good examples are danios and tiger barbs. If you get small groups of these fish, they will harass other fish in your tank. If you have a group of them, they pick on eachother instead of the other tankmates.
Exceptions: The inch per gallon rule is of course a guideline with many exceptions. This rule does not apply to goldfish. Goldfish need much more gallonage per fish, usually 20 for the first goldie and 10 for every subsequent goldie. Just because you have a 10 gallon tank does NOT mean you can put a 10 inch oscar in it. Use common sense. It's also not a good idea to put smaller fish in a tank until they "outgrow" it. Smaller living quarters often lead to stunted growth in fish. This sounds fine and dandy, smaller fish, what's the problem? Well, only the outsides of the fish stop growing, the insides continue. Eventually, your fish will die as its organs become too squeezed inside of its body, literally being squeezed to death. Not nice.
Please do thorough research on the web for any fish you plan to purchase. Do not add more than 1 or 2 fish at once, and of course, cycle your tank before adding ANY fish.
Disclaimer on Fish Store Advice: Fish stores/Pet stores run a business. Their job is to sell products and livestock to make money. What's their primary goal when you walk into the store? To sell you as much "stuff" as possible. Fish store employees often don't know anything about the species they are selling. Remember, they may even earn commission based off of how many fish they can sell you. Please do your own research. If you still don't know what to add to your tank or what a species needs are, fish forums are a great resource. is a helpful site full of knowledgable people with neutral opinions (they aren't selling you the fish). It's very helpful to post a question there about a product or item the fish store is trying to sell you, just to see if you do in fact actually need it.
