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How many pygmy corys can I keep in a 55 gallon 48" x 13" x 20" with 2 L-260`s as the only other bottom fish?

How often do you do water changes?
Is it a bare bottom tank?
Fully planted?...Planted with fast growing plants?

If you use the 1" per gallon rule it would be around 40 cories.

Cheers, Whitepine

water change once a week 35-40%.
Gavel with lots of driftwood and different size rocks and caves.

pygmy corys? These guys are only 1/2" big! You can probably get away with more than 40.

is listed in the cat-elog as 1.12" long. That may well be longer than they normally grow, but I would think that one that is 0.5" long is still not fully grown. You can't stock the tank based on the fish's current size, but the size it WILL be when it's fully grown. Other small cory's (C. Hastatus and C.Habrosus grow another tenth of an inch or two.

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Mats

Hi. I'm not a big proponent of the 1" per gallon rule - which has been around since the boom of the aquarium hobby in the late 40's and early 50's in the U.S.. This was before the advent of all the technological marvels employed in today's fish keeping. As an experiment, and to prove a point to a doubter, (doubting the Guppyman? Yes, unbelievably, it happens), I have on more than one occasion kept 60 adult guppies in a 10 gallon tank. I kept it beside a tank containing 20 of their siblings. The ONLY thing I did differently, was in the tank with 20, I changed 20% of the water, every other day. In the tank with 60 I did a 30% water change daily. After reaching maturity, there was NO difference in size, health or anything else that I could see between the 2 groups. Personally, I would have NO problem putting 200 C. hastatus or C. pygmaeus in a 55 gallon tank. I have 30 in a 10 gallon tank, now and they are perfectly healthy. Just my 2¢, but putting less than 50 in that tank, you'll be hunting for them. Put 100 or more and you'll be mesmerized. "Life is short - go long." - Frank/Guppyman®

P.S. Just my opinion. No 'flames" please!

I have three pygmy babies among my other cories in my 55. I think they're too active for anyone to be trying very hard to see them. As small as they are, they really know how to move.

Yes, we can cheat the 1 inch per gallon rule (that's about 2.54 cm per a bit more than 4 liters), but it's more work, more equipment (sometimes), and probably not going to make most fish happy.

On the other hand, with cories, more is always merrier.

The question "How many (whatever species) can I put in a ? gallon tank" comes up time and again. Personally I think using a gallon as a measure is not a lot of good on two counts.
1) the US gallon is only 3.785 litres and the imperial is 4.546 litres, almost 3/4's of a litre more, so the difference between the two 55 gallon tanks is 11.0 US or 9.2 Imperial gallons and never mind the 55 gallon tank I would comfortably keep 20 C. pygmaeus* in the difference between the two measures.

2) It is the surface area that determines the oxygen absorption into the water and therefore governs the amount of fish it will sustain, for example take two tanks of equal dimensions 24"L-12"W-12"H and 12"L-12"-24"H both hold the same water but the surface area of one has twice the oxygen absorption area as the other.

I know the use of air stones and filtering systems will increase a tanks capacity and there are lots of formula for working out so called capacity, but if you use the formula that a fish to be comfortable, should have a minimum tank size of 5 times its body length long and be twice its body length wide, the above 24" x 12' tank would house 25 full grown C. pygmaeus and it would not really matter if the tank was 6" or 12" deep.

Ian

Ian,

Thers's some good points there! [and the other post on tank-size was also well pointed out].

When it comes to MOST catfish, volume isn't a particularly good measure for how many you can have, because they are primarily bottom-living fish, so unless you have a weird tank-design [1], you won't get more fish in with a taller tank than in a shallow one, and for cories, 5-6" depth is certainly sufficient.

In any stocking scenario, you'd have to consider the level at which the fish lives and their need for space as well as the total tank volume [and filtration, water change frequency, individual fish needs, and several other things].

[1] One way to enlarge the floor space would be to have shelves in the tank that cover almost all of the bottom area, and either a small gap at the front/side, or some holes for the fish to enter the next lower/upper level. I don't know if this actually works, and I certainly have never seen such a contraption...

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Mats

new2Lnumbers wrote:How many pygmy corys can I keep in a 55 gallon 48" x 13" x 20" with 2 L-260`s as the only other bottom fish?

You say "bottom fish". How many fish total in the tank or is it just the corys and plecos?

MatsP,

To me stocking levels are dependant on the oxygen absorption capabilities of a said body of water, regardless of the position a or several species of fish prefers to reside in. Having species that reside at various levels in an aquarium may very well be aesthetically pleasing but I don't think it has anything to do with the capabilities of a body of water's ability to sustain a specific number of fish.

Ian

Coryman wrote:MatsP,

To me stocking levels are dependant on the oxygen absorption capabilities of a said body of water, regardless of the position a or several species of fish prefers to reside in. Having species that reside at various levels in an aquarium may very well be aesthetically pleasing but I don't think it has anything to do with the capabilities of a body of water's ability to sustain a specific number of fish.

Ian

As we started out, the matter of stocking levels, if you want to be precise about it is very complex.

For fish that live happily together (such as Cories), oxygen levels would be one of the important ones, filtration capacity another one [which is indeed related to the oxygen levels, since the nitro-cycle uses oxygen to conver NH3/4 -> NO3].

Other fish that are territorial, you also have to respect that they need their own space, which may be related to the level that they live at. In this case, some other specie of fish may well fit in together, either because it's beign ignored due to not seen as a "threat", or because it lives at different depth and thus aren't in the same territory.

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Mats

new2Lnumbers

To get the full picture and to get back to your original question, what are the total inhabitants of your 55 US Gal tank, how is it filtered and what are the water conditions.

Ian

I'd also keep in mind that you do not want a tall tank forthese guys. The Pygmaues and Habrosis will not be very happy trying to get to the top of a 40-gallon tall tank. It stresses them out and that's not good!

Thanks,

Scott

Pygmy cories have to swim up to the top of the tank to get oxygen right? I was seeing this a lot and i thought my oxy levels were low, but someone at my lfs said they need to do this. The pygmies do it more than the habs., and i ve been having trouble keeping the pygmies. Ill buy 6 at a time and only 3 maybe will live. All my levels are fine, and my other fish dont bother them. Are they just a weak species or hard to keep. Help please cause i love these fish, and i want to have a huge shoal for my 120 gAL soon.

suburbanlad,

Corydoras pygmaeus must be the easiest of all the Cory species to keep. You say all the conditions are fine, but you don't actually say what they are and with all due respect they may be fine for some of the tank mates but not necessarily right for the pygmaeus.

A temperature range between (21ºC & 24ºC 70ºF & 75ºF) is best they do not like it to warm.

Ian

All brochis and corydoras species will swim to the surface to grab air. Since they have a devolved swimbladder, they aren't able to use the swimbladder to get to the surface, they will have to SWIM up there. If the tank is fairly deep, and the cory's small, they will not be able to swim all the way without getting exhausted.

Small cories in a big (= deep) tank is not a good idea.

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Mats

Sorry MatsP,

But 20 inches of water might be regarded as deep for aquariums, but it is not in regard to natural water courses, in fact that is relatively shallow and I cannot see any problem with any species of Cory in that depth, in fact by the time you have removed the depth of substrate and the distance from the water surface to the top edge of the tank from the equation I would not mind betting that the water is not even 17 inches. Admittedly in nature the margins my taper in depth to zero, or only an inch or two, but very few will inhabit the extreme margins as a norm, but move in and out depending on the conditions, food availability and time of year. The only real problem I see with C. pygmaeus in this particular set up will be if the water is kept to warm, above 23º C (74º F).

Ian,

Agreeds with Ian. 20 inch should not be a problem with any corys. They are fish and are experts in swimming easily !

Going up for a gulp of air over 30 or even 50 inch often should not even be a problem at all.

Do a lot of cories have reduced gills if they are obligate air breathers?

The air taking has got nothing to do with the gills, the air bubble is swallowed and sits in the gut where it aids balance much like a swim bladder. While there the oxygen is absorbed through the gut wall and when it is exhausted the remaining gas is expelled through the anus, usually at the same time the fish returns to the surface for another gulp of air. If the oxygen content in the aquarium is depleted the trips to the surface may increase. Some species have the ned to do this more than others.

Ian

The air taking has got nothing to do with the gills

I know that, but what i meant was:

Animals, whose environments change, or change to suit new environments will adapt new strategies to deal with this, ie air breathing via the gut when DO in water becomes too low for gills to be effective.

When this happens, the original organs (in this case the gills) become vestiges, or are sometimes completely lost (ie eyes in Astyanax fasciatus mexicanus).

This of course wouldn't happen if this adaptation was used seasonally during hot weather, which i suspect would be the case with Corydorus?

However, if they are facultative air breathers (as i've supposed above) then why are people (myself included) reporting obligate air breathing in the aquarium? Why would they have to use their gut for air breathing when there should be enough O2 in the aquarium for gills to function?

I work on the assumption that there is "enough" 02 in the aquarium, as the other fish don't seem to be suffering from low DO stress.

from the replies i think the problem is my temp. My water is at 79-80.5, ph is 6.2-6.5, and 3dkh. I keep sa dwarfs and the cories in a 10 gal. There is no way they can do 80 degrees huh? Damn, those cories are my fav. I just picked up a cory that i forget the species name but it was also labeled violet eyes. Pretty small and cute. The species name began with an s, corydoras s... violet eyes. Its right on the tip of my tongue. Im upset that i wont be able to keep the pygmies.

Corydoras similis is the name I think you are looking for. They are a species that grow to around 2" - 2 1/4" (55.0MM) SL.

Ian