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For a few weeks now I've been curious about my Corydoras melanotaenia, in particular their size.

I originally only had 2 of them, I purchased a secondhand tank off ebay in Jan 07 and they were in it, I didn't think to ask at the time where they got them from or anything like that. Anyway they lived in a 66G for a few months before I got the tank that much I do know, then when I got them I put them into a 15G on their own(the larger tank had predatory / aggressive fish in). They lived in the 15G for about 4 months with 4 C.Aeneus corys until I got them an 18G, they all lived in that tank for approx. 5 months and then went into a 30G, they moved into their current 35G home back in january. I'd been looking for more Melanotaenia the whole time but my lfs only stock the more common corys. Anyway I managed to locate some more Melanotaenia by chance when I started going to a nearby Maidenhead Aquatics, they had some wild caught ones in so I purchased 3. As I said at the beginning of this post I'm very curious about the difference in size, the wild Melanotaenia are twice the size of the 2 I had originally and I wondered why, is it just that wild fish are naturally larger or could the 2 originals I have be some sort of Aeneus / Melanotaenia hybrid(long shot) or are the 3 wild melanotaenia not melanotaenia at all and are actually a brochi that looks similar? I have alot of pics, most of which are blurry but you can see the size difference, the 3 wild caught were very dark when I got them but 2 of them have lightened up alot(probably because of the light substrate).

Here are some pics of the original 2;










some pics of the newer ones;





some pics of the new and old together so you can see the size difference;







This is probably the best for showing the size & colour difference;




Also another question, I would at some point like to get more of them as they tend to be alot more shy then the Aeneus so I figured a larger group would make them feel more secure and perhaps they would be a little more outgoing. I wasn't sure if I had the room footprint wise for more corys,ammonia / nitrite are always 0 and nitrate stays below 10.

The tank is 39" x 15" x 15", external filter rated up to 80G tanks, fairly well planted(see pic below) the inhabitants are as follows;

6 x white cloud mountian minnows(hoping to get another 6 in a few weeks)
5 x C.Aeneus
5 x C.Melanotaenia
7 x Otocinclus



I was thinking another 3 Melanotaenia at the moment but eventually they will all be moving into a 4ft x 12" x 18" tank(hopefully by the end of the year) so I'll be able to get some more Aeneus, although I like the Melanotaenia so much I'm thinking of finding a new home for the Aeneus and just having one large group of Melanotaenia.



Thanks for reading

Hi Azaezl-
I'll not try to answer your stocking question as I tend towards moderately overstocked tanks myself (usually accidentally through fish breeding and having to move fish around in my tanks).

However, with regard to your new fish being larger than the older ones, I've noticed a lot of jumbo-sized wild-caught Corydoras of various species coming into the UK in the last 6 months or so, which seem to be far bigger than most of the tank-bred (or young wild-caught) specimens seem to get in aquaria, even with low stocking densities and lots of food. Whilst corys are quite long-lived, I always prefer buying young fish to maximum-size fish, and the problem with buying fish at their ultimate maximum size is that they could be quite old- you never can tell. However, I do know a few people who've bought large corys recently and they've bred them successfully, which suggests that most of them aren't ready to draw their pension yet!

In your 39" tank, you could easily get 50 more corys in there I would think.

Thanks for your reply carp, I guess they are just unusually large, I did notice alot of the wild caught corys in that shop were very large.

Wow zeny! That many? I'd like to believe it but how on earth would there be enough space for that many more, just doesn't seem possible to me, there's only 10 in there at the moment and that looks ok, I was thinking another 5 or 6 would be the maximum, at least that's put my mind at rest about getting more

I tend to stock over-heavily, which is why I didn't want to comment on the stocking densities, but my (overstocked) 48"X12"X18" tank has 20 Brochis in it (3 parents plus 17 progeny), plus endlers and apple snails. If corys are the main stocking for the tank I'd have thought 10/15 corys would pretty much fill it, unless you want to do 40% water changes every few days like I have to!

I do 25% bi weekly water changes, mainly because I'm dosing tropica plant nutrition+ and it recommends a 25% weekly w/c, but I prefer to do it twice. I figured 50 corys may be a little bit too much in my tank. I think I'll get 3 more melanotaenia & 3 more aeneus & bump the white cloud numbers up to 12, this isn't there permanent home, hopefully they will be going into a 48x12x18 in a few months. It wasn't so much the water quality that I was worried about because I overfilter and as I just mentioned I do frequent water changes, there's plenty of live plants so the water is fine, it was just the issue of space for them.Thanks for your help carp

12 to 20 should be plenty of them for your one meter long tank. That is a large enough groups to whip up enough male competition if the females become ripe with eggs. Keeping more would be fine if your tank was in a fish shop and fish were being sold and removed but for any hope of breeding, a lesser number would be better.

I may just go with more melanotaenia as they are more shy and I would like to try to breed them but I understand it is a little more difficult to breed them. Maybe another 4 for now and once I put them in the 48" I'll get another 2 and get another 2 aeneus. The aeneus seem quite happy in their group of 5, they breed on a very regular basis(I leave the eggs for them to eat though) so I may as well leave them as is.