# Fish for 2.5 gallons?



## Bonefish

I'm sad to say that last night, my ancient-yet-awesome betta Rilix, same as pictured in my icon, died. She leaves behind a 2.5 gallon planted nano, which seems ridiculously empty without her. I'd like to eventually restock it with new fish in a few weeks, which leads me to ask: what kinds of fish can thrive in a 2.5 gallon? 

The tank is low light, no fert, heated, and filtered. It's fairly densely planted and has a piece of driftwood in it (the old photos in my thread are no longer accurate-- the tank now has bamboo and no longer has an anubias, among other things). Other residents are a few trumpet snails, a ramshorn, and several RCS.

Here are some of the fish I'm considering:


Another Betta splendens
Some other Betta species -- Imbellis, Mahachai, and Channoides are of particular interest
Endler's livebearers
Feeder guppies or fancy guppies
Boraras brigittae
Celestial pearl danios/Galaxy rasboras
A few Otocinclus
A few pygmy cory cats
Which of those do you think would be okay in a small nano? Which would you nix from the list? Any other stock suggestions?


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## DarkMatter

Sorry for your loss. I would say Pygmy Corys, they are my fav fish to watch, mine always hid at first but now are always pearched on plants or out searching for food.


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## Axelrodi202

I'd advise against the CPDs. They tend to be rather skittish in small tanks. If you choose the Endler's livebearers, make sure you only get males or you'll soon have too many fish in the tank. Personally, I would choose the Boraras, but most of the species on your list are pretty good choices.


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## red fish blue fish

Sorry to hear about the loss of your betta. 

I'm not a veteran of fish keeping, but I've been reading up on fish for small tanks pretty extensively over the past month. Honestly, the only thing I know of that would be suitable in such a small tank is another betta.

From what I've read, all the fish listed except for betta are social or shoaling fish. Meaning they're meant to be kept in groups of at least 3-6, often more for fish like danios/rasboras. When considering what kind of fish "fits" in X size tank, I've found it helpful to read about how the fish needs to be kept, their waste load, activity level, and how quickly they reproduce.

For example, just about every source I found has said cory cats or otos should be kept in groups. Sure, you might be able to physically house 1 single cory/oto in a 2.5 gallon, but that doesn't actually work out in reality. And 3-6 of them in a 2.5 gallon would be well past the bioload capacity, IIRC. 

Another example, any kind of live bearers (like guppies) can reproduce like mad. So your 3 little live bearers that seemed ok in a 2.5, suddenly double in short time and now your tank is over crowded. In some cases you can try to have a group of single-sex fish, but keep in mind that many male fish (and females as well) can be very territorial and are not happy sharing a small space with 5 other males. Also, it can be really hard to tell the sex of small, young fish to be able to set up a single-sex tank. And I wouldn't count on your LFS being able to tell the difference, unless it's a really good store.

A final example, some fish may be very small and it may appear that a group will "fit" in a 2.5 gal tank. But it turns out that those very small fish are active swimmers, which means they're going to need more space than just what looks good on paper (like 1inch=1gal). IIRC the danios and Boraras are swimmers.

From reading up, it seems that ignoring these basic requirements and behaviors of the fish can create a situation where the fish are continually stressed out or agitated, which can lead to health problems. So it's best to go bigger. 

What about moving up to a 5 gallon or 10 gallon?


ETA: forgot to mention that I have a 2.5 gallon as a temporary tank and the size/type of fish may also depend on your type of filter. Depending on the brand/model, a submersible/in-tank can take up A LOT of room in a 2.5gal, reducing the swimming and hiding space for your fish.


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## Tenzo

I'd say Boraras brigittae (Chili rasboras), Pygmy cories, or Heterandria Formosa (Least Killifish). Though for the chili rasboras, you might want to have a bit more shady areas, or stick in some floaters. Though for you current setup, the pygmy cories would look awesome!


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## Captivate05

Boraras briggitae are ridiculously small. They are very bright and colorful though, IMO a good choice for a pico tank.


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## TeamTeal

shrimps?


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## lauraleellbp

I'd absolutely get a Betta imbellis- I came sooooo close to getting one for my 10gal!

Wild-type bettas are definitely a passion of mine. =)


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## Bonefish

Awesome suggestions and advice, guys, thanks.  

*DarkMatter *- I saw some pygmy cories at my LFS a few years back. They were too cute! 

*Axelrodi202* - I'll nix the CPDs from the list, then. That's fine by me; they weren't a top choice of mine, and I have no clue where I could get them locally either. Yeah, I'd definitely be going for an Endler's/guppy frathouse if I go with any livebearers. I learned my lesson about livebearers the hard way when I was a kid.
*
red fish, blue fish* - thank you for the thorough write up! The shoaling issue is exactly my main concern. For example, I've read that otocinclus like to be in groups of 5+... no way I can do that in the nano. I've successfully kept three male feeder guppies in a 2.5 gal; I may try that again, or go with some kind of betta like you said. The feeder guppies weren't skittish at all, just a bit territorial. They kind of partitioned the tank so that the most dominant guy owned the open space in the center, and the least dominant got to chill in the corners. Never hurt each other, though.

Ah, yeah, the active swimming issue is also important. Back when I first got into the hobby (circa early 2006), I asked a person at Petsmart which species I could put in a 2.5 gallon. They sold me some leopard danios. Of course, I found out a few weeks later that leopard danios live in fast-moving streams and prefer 20+ gallons. Oops! (They eventually got upgraded to a bigger tank, no thanks to Petsmart)

I wish I could upgrade to 5-10 gallons, but I'm constrained by space on the counter top at the moment. 

Good thing about the filter is that it's a Red Sea Nano -- doesn't take up much room.

*Tenzo* - I just Googled the _Heterandria formosa_... tiny fish! Very adorable, and their silver colors would look great in the tank. Gonna add them to the "maybe" list!

*Captivate05* - I'm charmed by their size and color too. As long as their swimming needs don't exceed the capacity of the tank, I'd be happy to get them. Has anyone here had B. briggitae thrive in a nano?

*TeamTeal* - got about 5 RCS chilling in it already. I'm sorely tempted to add some regular bee shrimp as well, but I feel like that would leave the entire upper half of the tank very empty. That's the only reason I'm keen on a fish or two.

*lauraleellbp* - I've never owned a wild type betta, but I've fallen in love with them from the pictures I've seen on Google. They're such stunning fish. Do you think any of them would settle for a 2.5 gal? I'd love to pick up an imbellis. Problem is, I have no idea where to get an imbellis, and I want to get captive bred, not wild caught. If you have any betta resources to share, I'm all ears!

Do you think a B. simplex would work in a nano? I wasn't considering them before, but after following the link in your signature, I'm curious about the species.

_Updated fish list:_

Most likely -


Another Betta splendens
 Some other Betta species -- Imbellis, Mahachai, Channoides, maybe Simplex
 Boraras brigittae
 
Maybe - 

Heterandria Formosa
 Endler's livebearers
 Feeder guppies or fancy guppies
 A few pygmy cory cats


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## jclee

I think having all males of a small livebearers species is the way to go if you decide not to get another betta. I'll point out that boraras brigittae is also a schooling fish, so they probably wouldn't have enough space in the 2.5. I've got 6 of them in a 10G, and they're doing wonderfully in that, so if you ever do have the space to upgrade your tank, I'd definitely recommend them.


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## lauraleellbp

If you want more info and sources for wild bettas, try www.ultimatebettas.com. There's quite a few of those forum members who keep and sell wild-type bettas. I got my own B. simplex from brianjim on that forum (and he keeps and breeds tons of different wilds).

B. simplex are one of the smaller and easier kept species- I definitely think a male would work for your 2.5 gal.


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## BonesCJ

I keep a pair of White Cloud Mountain minnows in my 2.5 that I keep at my desk at work


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## DaveK

This is going to sound a bit off the wall compared with some of the more exotic fish mentioned, but I'd get a male paradise fish, either the red or blue type. Here's a link (offsite) - http://en.wikipedia.org/wiki/Paradise_fish


Easy to keep, colorful, its an anabantid like betas, and it's been in the hobby almost forever. What's not to like? IMO, if it were difficult to breed, it would be valued right up there with any other high priced fish.


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## wendyjo

Did anyone mention endlers? A group of males would be awesome!


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## shane3fan

Ive been advised in the past that a 2.5 gallon is too small for almost all fish. 

Im sure that is something that opinions will vary on. I do know that my 2.5g is very hard to maintain--the water quality, temp and parameters swing so fast that it is easy to lose control of and wipe out your livestock. Im thinking of doing a shrimp tank with RO water at some point with my 2.5, but for now it is a holding tank for plant clippings.


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## Bonefish

*jclee *- that's what I'm thinking. Last time I had feeder guppies, they stayed pretty small and seemed to be healthy. They get surprisingly colorful too! Almost like little Endlers.

*lauraleellbp* - Thanks! I'll head on over there to see what they've got. I'm seriously considering a B. simplex now. They're gorgeous, and according to the IBC site, they do fine in tanks as small as 2.5 gallons. I'm such a sucker for the wild-types.

*BonesJC* - ahh, I've seen those before. I keep getting them confused with rosy red minnows, which are a totally different deal (and definitely wouldn't work in a small tank). Don't know of my LFS carries the white clouds, but I'll keep them in mind.
*
DaveK* - whoa, gorgeous fish! I wonder if it would eat all the RCS. I hadn't though about gouramis, but come to think of it, aren't sparkling gouramis considered decent nano fish as well?

*wendyjo* - Definitely considering Endlers. 

*shane3fan* - that goes with what I've read, too. From what I've seen discussed around here and other sites, 2.5 gallons is kind of the bottom limit for keeping fish, and even then, your fish selection is extremely limited. So far I've only successfully kept bettas and 3 feeder guppies in 2.5 gallons; but I haven't tried any other species yet. I'm probably going to go with some kind of betta again. They seem to be tolerant of variation in water quality, and they don't add very much to the bio load.


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