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Charlie 08-05-2009 04:29 PM

20L; how many cories?
I have a 20g long style tank that I have 6 cories in. They are emerald/bronze cories. After refurbishing their tank, I have the itch to add some more, as it looks very bare in the tank. How would you recommend doing this? I haven't bought new fish for this tank in a long time--it's been a year since it was established, and I had the cories in a 10g before that.

All of the tank parameters come out to being fine. I have driftwood and plants in the tank, lots of them (mostly java moss, I love the stuff). I was also wanting to add a bristlenose pleco, as I love them to bits, and my last one was lost in a tragic accident :(.

So.. how many more cories can I add, in addition to the pleco? I know it's usually a sort of trial-and-error. I was thinking of adding 6 more cories, probably of a different species, but I'm not sure yet, then adding the pleco later.

Also... I have a 10g filter that's not doing anything at the moment. Would you guys reccomend installing it on the tank, in addition to the 20g filter I already have? (I might do this anyways, since it would make filter maitenance a lot easier without having to worry about one of the filters completely crapping out if I fuss with it).

Thanks guys..

aunt kymmie 08-08-2009 12:18 AM

If it was me (and it's not!) I wouldn't think twice about adding more fish but instead of adding more cories I'd add some mid to upper level swimmers rather than more cories. Don't the bronze max out at 3"? I'd do a small school (5 to 6) of some small type of tetra or rasboro. They produce less of a bio-load than the cories and would "fill" out your tank. I'd think you could also add the bristle, providing your diligent in your weekly w/c. Extra filtration can never hurt, IMHO.
Someone else will have a different opinion so please chime in. :-)

Byron 08-08-2009 10:55 AM

I'm with kymmie on adding some upper level fish. Corys can sometimes be a bit skittish when there is nothing moving about above them in the water; yours may or may not be, but corys are odd little fish that can suddenly change their behaviours, so for their comfort I would add some shoaling fish; tetras from SA or Asian rasbora are both good as kymmie suggested, as they are peaceful, colourful, shoaling (swim in groups) and active.

On the size of your "bronze corys", if these are a true Corydoras species they should max out at 2 inches. But most emerald corys sold in stores are not Corydoras but actually Brochis splendens, a closely related genus to Corydoras, that grow larger. There is some differentiation in the shape of the fins between Brochis and Corydoras, especially the dorsal which has more rays in Brochis, and a couple of internal bone differences that are not visible outwardly; but Brochis are just as peaceful as corys and share similar behaviours, but being a slightly larger fish they have slightly more effect on the bioload as kymmie mentioned. And she is correct on regular maintainance: weekly partial water changes with gravel syphoning are important because Corydoras and Brochis spend much of their time sifting through the substrate and can develop health problems (especially the barbels) if the substrate is not relatively clean and nitrates are not kept under control; and the easiest way to do that is with regular weekly partial water change of 30-40% of the tank volume. Use a good conditioner, as corydoras are sensitive to water quality and parameters, and do not tolerate chemicals (medications) very well.

On a scientific note, there is some thinking that Brochis is not a valid genus and the three sole Brochis species should be moved into the Corydoras genus, and with some of the larger Corydoras species (C. barbatus, etc) perhaps assigned a subspecies. Hasn't occurred yet as far as I know.

aunt kymmie 08-08-2009 10:57 AM

Byron- what are your thoughts on adding a bristle to this tank?

Byron 08-08-2009 11:03 AM


Originally Posted by aunt kymmie (Post 224460)
Byron- what are your thoughts on adding a bristle to this tank?

There are around 60 identified (named) species of Ancistrus, the bristlenose, and maximum adult size is approximately 15 cm (6 inches) for males, slightly less for females. Good algae eaters in a peaceful environment. Should work fine in a 20g long IMHO.


Charlie 08-09-2009 02:40 PM

I believe they are true cories. They have really not grown much since I have added them to the tank, most of them are 1.5-2". (Edit: Just looked up the brochis.. these are definitely NOT the brochis). I did already know most of the info you posted, but thanks anyways. I keep a good eye on the tank parameters, just because I love those little cories so much. Also, I don't have a gravel substrate, it's sand (about 3/4 inch, it's pretty shallow, and I sift through it regularily and it doesn't seem to become compacted enough to form nasty air pockets... plus the cories are always digging in it).

I'm kinda iffy on adding upper level swimmers to the tank. Frankly, tetras are not my favorite kind of fish. If I was going to add something other than the cories, it would probably be rams or some apistos (specifically cacatuoides, my favorite). I don't like boring "filler" fish, and having tetras in the past hasn't been the most fun. Perhaps I'll add the apistos now, instead. I've also been leaning towards getting more cories, but just getting pygmies.

About the skittish problem--I think the amount of overhead shelter they have is sufficient. It's not like I just have a completely open tank... about half of it is dense driftwood and plants, with just the middle being open sand. I don't really mind not seeing all the cories all the time, and they seem content being in the shade.

About the bristlenose: specifically albino bristlenoses, I recently found a friend of mine has two in a ten gallon that are getting too big (I think male/female.. with any luck), so I was going to take them off his hands (long story as to why they're still in a 10g..). So, 3-4 inches max (they are around 2" now).

soo tl;dr: Add a cockatoo cichlid (probably a pair, since I would have to get them online), 4-6 pygmies and 2 ABPs? Should I suck it up and add some ember tetras instead of the pygmies?

(thanks for the replies btw)

Byron 08-09-2009 04:57 PM

In some cases the "dither fish" are necessary in order to fully enjoy the behaviours of the main fish in the tank. But not always. A pair of Apistogramma cacatuoides or Mikrogeophagus ramirezi would be very nice in your setup, but I would certainly add a shoal of 5-6 small characins; these cichlids are territorial but somewhat timid when they feel alone, and there are many suitable fish among the characidae other than common tetras, like pencilfish and hatchetfish.

I obviously don't know your experience level, so pardon me if what follows is old news. Dwarf cichlids are very sensitive to water parameters and water quality, even more than corys in my experience. If your "emerald/bronze" cory isn't Brochis splendens then it is probably Corydoras aeneus which goes under the common name of bronze cory quite often. This species is able to tolerate the higher temperatures (80+F) which are mandatory for M. ramirezi but is also comfortable at the more normal community aquarium temperature of 77-78F which suits A. cacatuoides. As for the other parameters, A. cacatuoides occurs in Peru chiefly in the Rio Ucayali system, and has been captured in water with a pH of 7.6 and moderate hardness. These values will also suit C. aeneus; found in streams in Bolivia, Brazil, Ecuador, Peru, Columbia, Venezuela, Surinam and even on Trinidad, this species may have the largest range of any cory, most of which are endemic to a particular stream or system. While the waters will have considerable variation between all these localities, the fish has been commercially raised for many years and this is not likely to be an issue.

By contrast, M. ramirezi requires very soft and acidic water if it is to be kept in good health. The frequent demise of this fish in aquaria is almost solely due to its intolerance for water parameters that are not reasonably close to its habitat in the central Orinoco of Venezuela and Columbia. And this in spite of being commercially raised; it certainly seems to have retained its evolutionary programming.

Albino bristlenoses can reach five inches if properly maintained, so this will add more significantly to the bioload which is certainly a consideration with Apistogramma or Mikrogeophagus in the picture.


Charlie 08-09-2009 06:11 PM

Thanks for the informative reply. I had assumed that the apistos would be annoyed by a school of tetras, however I can see why it would be beneficial to have some. I do know that the rams are very sensitive, which is part of the reason I was thinking of cacatuoides. I have seen it proclaimed as the "easiest apisto".

So in conclusion... the bristlenoses will be added, then later, some ember tetras, and then finally a pair of cacatuiodes if all goes well. Thanks for the help.

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