Largest fish that can live in a 20 gallon tank.

[AquaticQueen]

I was wondering what is the biggest fish that could live in a 20 gallon tank. I know that my tank is too small for an angel or a discus fish but something not super aggressive and colorful would be nice. I would like to keep them with some corys and neons. I don't really want rams. Any ideas?

 

[TWiG87]

I’d say a max of about 3” or so. That leaves certain species of gourami, platys, mollies, some dwarf cichlids.

 

[JoshuavanWyk]

Apistogrammas are beauties!

 

[SnookusFish]

Bolivian rams?????

 

[JJfishes]

If you went to the pet store and asked, you could probably leave with about 12 red tail catfishes.

 

[kallililly1973]

Platy, sword tails, Mollys get to a decent size . Keep in mind they have a reasonably big bioload so don’t get too many if u go this route. Also if u get females chances are they will b pregnant and release dry and fill your 20 up pretty quickly

 

[jake37]

Cruel - very very cruel....
--
In case you don't know red tail catfishes are really nice looking fishes that are usually around 2 inches in the pet shops. However, they do grow to be around 50 inches when adults.....

If you went to the pet store and asked, you could probably leave with about 12 red tail catfishes.

 

[JJfishes]

Cruel - very very cruel....

sorry.

 

[Joshaeus]

'Largest fish for a 20 gallon'? Is it a 20 long or a 20 high? Most fish need much more floor space than depth, so a longer, wider tank can hold somewhat larger fish than a tall tank with the same volume. I agree with the above, a pair or trio of 3 inch fish are probably the maximum for a 20 long...maybe something a tad smaller if you have a 20 high. I would not recommend mollies for this tank...most mollies can easily hit 3-4 inches (sailfins get considerably larger), are very active, AND females are usually pregnant when you buy them. If you get a territorial fish like dwarf cichlids or small gouramies, the fish are more likely to get along well if there is a lot of cover to break up lines of sight and define their territories.

 

[AquaticQueen]

'Largest fish for a 20 gallon'? Is it a 20 long or a 20 high? Most fish need much more floor space than depth, so a longer, wider tank can hold somewhat larger fish than a tall tank with the same volume. I agree with the above, a pair or trio of 3 inch fish are probably the maximum for a 20 long...maybe something a tad smaller if you have a 20 high. I would not recommend mollies for this tank...most mollies can easily hit 3-4 inches (sailfins get considerably larger), are very active, AND females are usually pregnant when you buy them. If you get a territorial fish like dwarf cichlids or small gouramies, the fish are more likely to get along well if there is a lot of cover to break up lines of sight and define their territories.

It's a 20 long.

My stocking plan is this:
8 neon tetras
7 corydoras elegans
Some centerpiece fish?

 

[Joshaeus]

Ah...that is helpful. HEAPS of dwarf cichlid species would do well in a 20 long as a pair/trio; you could even keep a small colony of some of Tanganyika's shell dwellers (which are not outrageously colorful but have intriguing behaviors). Leaving cichlids, other options include small danios and rasboras, small to medium sized gouramies (perhaps up to paradise fish, a favorite of mine...don't mix them with fish smaller than a large platy; they will hunt fish much too large to fit in their mouths!), small tetras, almost all of the killifish in the aquarium hobby (in many cases groups are feasible), NUMEROUS cories and other small catfishes, probably some more unusual options I cannot immediately think of...

EDIT: Your stocking plan sounds OK so far, though I would personally skip the cories and have a larger school of neons (perhaps a dozen?). However, I am not great about making specific stocking suggestions, so hopefully someone better at that than I can help you.

 

[ystrout]

You're pretty close to full capacity.

Some people say dwarf gouramis are okay in a 20 gallon. I had one in my 75 gallon and he used the whole tank and explored everyday. So I personally think they're best in larger tanks.

 

[AquaticQueen]

You're pretty close to full capacity.

Some people say dwarf gouramis are okay in a 20 gallon. I had one in my 75 gallon and he used the whole tank and explored everyday. So I personally think they're best in larger tanks.

Should I decrease the school sizes to,
7 neons
6 cory elegans (or a smaller species?)

 

[Joshaeus]

Should I decrease the school sizes to,
7 neons
6 cory elegans (or a smaller species?)

Personally I would just do one larger school. The more the merrier for little social beasties like these

 

[AquaticQueen]

I think I have come to a final decision.
14 neons
A pair of GBRs, male and female?
I am also considering a pair of peacock gudgeons.

 

[aoiumi]

Or.... you could do cories? I love the little guys. Will always recommend.

 

[AquaticQueen]

Or.... you could do cories? I love the little guys. Will always recommend.

Maybe.

Now I am thinking of doing an all guppy tank.

 

[ystrout]

Should I decrease the school sizes to,
7 neons
6 cory elegans (or a smaller species?)

I mean, you could... I personally think it's really cool to have a mid swimmer like a tetra and a bottom swimmer like cories. The entire tank is occupied and the cories will gladly eat the food that makes it to the bottom in addition to what you feed them directly.

If you don't do a centerpiece fish, you could even make those schools bigger. You could do 10 of each or so.

With a gourami or ram, you won't want to add more of them.

 

[AquaticQueen]

I mean, you could... I personally think it's really cool to have a mid swimmer like a tetra and a bottom swimmer like cories. The entire tank is occupied and the cories will gladly eat the food that makes it to the bottom in addition to what you feed them directly.

If you don't do a centerpiece fish, you could even make those schools bigger. You could do 10 of each or so.

With a gourami or ram, you won't want to add more of them.

So if I don't do the rams I could do 10 neons and 10 corys? Or if I did a smaller species of cory like panda, could I do more corys?

 

[JB92668]

fire mouth cichlids aren't to big but your better with rames

 

[ystrout]

So if I don't do the rams I could do 10 neons and 10 corys? Or if I did a smaller species of cory like panda, could I do more corys?

The low 20s of those kind of fish is fully stocked.

Have you heard of the "inch per gallon" rule? A lot of times, it's completely wrong. Most times actually. But when you're thinking about small community fish (under 2 inches) in a 20 to 40 gallon tank, it's pretty accurate. I'm talking from years of experience measuring stocking capacity based on fish comfort and nitrate increase by week.

If you have about 20 cories/tetras, both being ~1 inch and not requiring excess food like a puffer or gourami would, you'll be able to keep the nitrate under 10 ppm with standard 25-35% weekly water changes. If you get zebra danios instead of tetras, which are larger and eat more, you'd want to have a couple less. Say 7 to 8 danios and 10 cories.

Half of your fish would be bottom feeders and the other half would be mid level swimmers so it wouldn't feel overly crowded for them.

So if you're not considering a centerpiece fish, go ahead and use the "inch per gallon" rule. It just so happens to work almost perfectly for small community fish that go in a 20 gallon tank. But gouramis, rams, puffers, etc. will make the inch per gallon guidance be wrong. While a gourami or ram are only 2 inches, they produce the amount of nitrate that about 5 or 6 tetras would since they are so much larger by mass.

 

[BettasAreSuperior]

I think a honey gourami. Honey gouramis are more peaceful than most.

That yellow with red and blue with corys! Bam! great!

 

[jkkgron2]

I have peacock gudgeons! Amazing fish, do best in groups or pairs. They’d do great with 12 neons and maybe a few nerite snails to help eat the algae!