What fish can I keep in a 2.5 gallon tank?

Question

I've got a 2.5 gallon tank with filter and heater. Right now it contains a female betta and a common goldfish. What other fish can I keep in there? Or, if I take both the betta and goldfish out what fish can live in that size tank? Is it possible to have any type of shark in it?

Answer 1

I would remove the goldfish now as they grow WAY too large. Here's a copy of a recent post I made about small tanks, hope it helps and good luck with it!

Most aquarium keepers will try to tell you they are good for nothing or at best good for a single betta. These people couldn’t be more wrong. They are not usually good for a betta, but they are good for a surprisingly large variety of fish once properly handled. A wise man once said “Great things come in small packages” and that is what we are going to explore in this article. The great things that can come of one of these micro tanks.

One of the best ways you get one of these hidden gems is at a yard sale or flea market. Usually they can be had for just a very few dollars and might be missing some of the parts you don’t care about in the first place. Once you have your little tank, clean it up and make sure it doesn’t leak. Then sit back, look at it and imagine it is a real honest to goodness aquarium in the conventional sense. What would you need? Heater, filter, lighting come to mind first, so let’s explore those.

Some of these little tanks come with an undergravel filter that can be a very good solution to filtering. Commercial power filters are available for very small tanks and would make a great choice. They come in both internal and external configurations and can do a wonderful job of filtering you micro tank. Larger power filters are no good as they would turn such a small tank into a whirlpool. The same is true for a canister filter. Of course, if you are handy with bending and forming plastic you can make a very small power filter for the tank, but that’s another article.

Small power filters can pose the problem of a strong directed output that causes strong currents in such a small tank. This can be managed by attaching a piece of tubing to the output with holes drilled along the length to break up the flow or by directing the out put of the power filter down through an undergravel plate. The second option adds the gravel as a bio filter helping the tank and helps prevent the build up of waste in the gravel.

Let’s assume you have an under gravel filter and very small air pump. Then your good to go. If not, what do you have? Most likely a small box filter that sits inside the already too small tank, right? Not a good option so let’s tank about replacements. An undergravel filter plate is very easy to make and can be run from the same air pump used to power that box filter or you can replace the box with a commercial or homemade sponge filter. The main point here is you need a very small filter with a quite low flow rate that will support the bio load of the few fishes you place in your tank.

I have seen these little tanks outfitted with power filters custom made for them, reverse flow undergravel plates and a whole host of other options created by the owner so don’t be afraid to go out on a limb and take matters into your own hands when it comes to a filter. As it’s commonly included or easy to make if not included let’s assume you have undergravel filters for your tank. Undergravel filters have their limitations, but provide excellent bio filtration and reasonable mechanical filtration, but of course no chemical filtration.

Lighting is usually very limited due to the short size of the hoods that come with these tanks. Again, you can modify the hood. Most can be made to hold a very small florescent light which is a nice step up from the night light many of these come equipped with for illumination. Grab a measuring tape and get a small florescent light from the hardware store or department store that will fit the space and go to town with the hot glue gun. Any decent “crafter” can put this together in no time.

Heating is the easiest answer as you can buy commercial heaters as small as 4 watts through a wide variety of outlets.

So now you have your little tank already to set up, you have your equipment, decided on your gravel color and accessories (very few I hope) and need to figure out where to put it. Here’s another great benefit of your new tank, it can fit almost anywhere! The only thing to really avoid is a draft or direct sunlight, just like this tanks big brothers. These little guys are perfect for a book case, the corner of a desk, just about anywhere you want a little color and activity. So the next big question, what in the world can you keep in about 2.5 gallons?

Again go back to your mental image of a normal sized community tank and now think smaller. Even smaller. As small as you can get. Now you have it, the same kind of fish in the same ratios but the smallest varieties out there. Dwarf cory catfish, Sparkling gouramis, most any of the smaller killifish, small tetras, Least killiefish ( which is actually a livebearer) all make good bets for a micro community tank. Toss out any “rules” you know about inches per gallon and just keep the tank to about 5-6 fish. Another choice for tank inhabitants is to go for a species tank. A single pair of a small fish can not only live but thrive and breed in your new micro tank. Killifish, sparkling gouramis and Least Killifish come to mind first, but there are obviously many more choices. Now for maintenance issues.

With quality lighting, a reasonable variety of plants are candidates for a mirco tank. Jave Moss, Jave Fern, Bladderwort, crystalwort all come to mind. Several of the bunch plants available at pet stores could be included as well if you are ready to do lots of pruning. There are also several varieties of small anubias sp. And even some micro swords available to spruce up your tank.

Maintaining a micro tank is not really any different than a full sized tank. Just remember the rule bigger is easier. This means the larger the tank the easier it is to maintain all other things being equal. Yes, it will require lots of frequent water changes, but those you can do with nothing larger than a clean gallon milk jug. Other than being very careful with your water changes anything else you would do for your fish in a big tank you do in a small tank. A micro tank is more work than a larger tank, per gallon at least. So is it worth it? That’s up to you. It can often be the only way to bring your happy to work with you and for some people is the only reasonable way to keep a tank in a small apartment or flat.

MM

Answer 2

You can't have anything in that tiny tank but the one betta and it needs a heater and a filter. Take the goldfish out because they are coldwater fish and produce a lot of waste and need to be in a much larger tank. The goldfish alone needs a minimum of a 10 gallon tank. No, you can't have a shark and you can't have any other fish. No fish can live in that small of an aquarium, and even a betta really shouldn't but it would be okay. Get another 10 gallon tank for the goldfish and nothing else can be put in with the goldfish either.

Answer 3

You really need a larger tank for all fish. The fish grows,and if the tank is small the fish will die. Because they have no room to grow.
Right now I think two is really too many fish in your tank size. I would only have one in the size that you have now. I would save up some money ,and purchase at least a 10 gallon tank.I would not put no more than 3 fish even in the 10 gallon tank. I really know about fish I did have at one time 1 55 Gallon tank,1 30 long tank,and 1 10 gallon tank.I love fish. You may want to talk with your local pet shop about fish also.I like the black mollys,and the kissing fish,and silver dollars,and angels,and bleeding hearts,painted glass fish,and of course gold fish.

Answer 4

The goldfish doesn't need heated water but it won't kill it. Take out the goldfish and put it in a bowl made for it. Could get a red-tail shark. They don't tend to be really aggressive and are pretty to see. They are a bottom feeder. Also small neon tetras would look very showy. Are bright blue/red combo. Maybe three of them. How old is your tank? Don't add all the new fish at once, and use Start Right or another good stress conditioner every time you put in a new fish or water change.

Answer 5

Bettas are your best bet. One male and one or two females at a time is well enough.

That common/comet gold fish will out grow that tank if it lives longer than a year. I have seen them at over ten inches after that length of time. Sorry to say but I'd get him out of there. The tank is too small for a gold fish.

Kev

Answer 6

I agree about removing the goldfish, but my reason is that they don't do well in heated water. I like neon Tetras, the give a nice glow to the tank. I think 2.5 gal. is pretty small for even a tiny shark, and besides, I don't know if there is such a thing as a freshwater shark.

Answer 7

You can keep gold fish, black mollies, and guppies. Take that betta fish out completely because she will eat your other fish. The betta fish should live seperatly. I had a betta fish once in a tank with two gold fish and two guppies. The betta fish ate my guppies and bit the tails of my gold fish. I wouldn't put any sharks in the tank either.

Answer 8

well i would remove the goldfish they give off to much ammonia the betta with a few plants would be nice

Answer 9

that size tank is good enough for 1 betta.

Answer 10

a bubble eye fish and no it is not possible to put a shark in it