Congo Tetra eats Neon Tetra

[BumerStinky]

So I had a couple of Congo Tetra's for a while, and have now finally got 12 Neon Tetra. There are plenty of plants and hiding areas but the Neon Tetra's are very small and the Congo's being fully grown have become a decent size. After a few hours I saw one of the Congo Tetra's eating a Neon Tetra, perhaps if I feed them more often they will leave each other alone in future? Any ideas anyone?

 

[Byron]

I have not witnessed any of my Congo Tetras--and I have had a group now for four or more years, and many years ago had a group--even looking a small fish, but this likely has something to do with their environment.

Congo tetra, like neon tetra and any tetra species, is a shoaling fish; it lives in groups of usually hundreds, so it must have a number of individuals in an aquarium. I tend to go for 8-10 Congo, and more than this for the smaller tetras, provided the tank is large enough to accommodate them (I'll come back to tank size). Two Congo tetras will be under stress. I'll come back to stress too.

Tank size is important obviously, but here again too small a space to suite the fish's natural behaviours and interactions can cause stress. Congo tetra need a 4-foot tank, and must be in a group of at least 6 or 7, preferably a few more.

Now the stress. Both of the above issues cause stress because the fish's expectations which are programmed into the DNA of the species are not being met. Scientific studies have now determined that stress usually causes increased aggression; naturally aggressive fish become more aggressive, and normally peaceful fish become aggressive to some degree. Sometimes the opposite occurs, where an individual fish may become stressed to the point of withdrawing and slowly weakening to death. So only having two is stressful.

That means that the Congo may show their frustration by attacking a fish they otherwise would leave alone. I have Diamond Tetra in my tank with the group of Congos, and the Diamonds are prolific spawners; I had 7 Diamonds when I added them to the tank last year, there are now just over 30 with the fry that have managed to survive. Point is, the Congo don't seem interested in the fry, as I have observed fry as small as 1.3 cm swimming near the fully mature 4-inch Congos.

Having said that, and without knowing the tank size and other environmental info (aquascape, parameters, other fish), the neons may be so small they are targeted. But it also may be more an issue of a weak neon being grabbed. Feeding is not likely the answer, as too much food (and it is easy to overfeed fish) means other negative issues with the fish and the system.

Byron.

 

[AbbeysDad]

I dunno....big fish eat little fish. Some parent fish will eat their own fry. It happens. I also have seen large fish totally ignore small food size fish swimming by and parents that really care for their fry...but I've also seen big fish eating little fish. It may be aggression or stress as Byron points out....or it may just be a snack! 'Stuff' happens!

 

[NickAu]

or it may just be a snack! 'Stuff' happens!

Yes, Betas hunting and eating Malaysian trumpet Snails, and they go nuts over few day old guppy fry.

 

[BumerStinky]

Thanks all, the Congo's seem to have settled down now. I wonder now if the Neon Tetra was just not in good shape and when I got it home from the shop it was already on it's last legs, as the others are all being left alone.

I have had my two Congo's for a while now and were doing fine, but they were used to having most of the tank to themselves, maybe got a but stressed when all their new friends arrived. Do you really think they will be stressed just the two of them, apart from that one incident they seem fairly well adjusted, occasionally darting about but mainly lounging amongst the plant life.

I had a few issues getting started and a number of fish died, I bought the aquarium 2nd hand and have now upgraded the filtration so it is getting a lot of filtration now for 60 L tank, I was a bit worried about the flow rate and pointed the water circuiting back in at the tank wall, but the fish seem to love it and will often pop over to swim about directly where the flow is.

I have 2 guppies ( I did have about 8 but only 2 made it), 2 molly's, a single swordtail, a small angle fish, a single bistlenose, the 2 Congo and 11 Neon.

 

[BumerStinky]

My Tanks probably too small for Congo, the guy in the shops answer to all my questions when first buying the fish for my new tank was almost always 'that will be fine' which probably explains why so few made it, well live and learn, hopefully they are gong to be ok now, they seem to be acting ok.........I am also looking to buy a house so after that I will upgrade my tank

 

[Byron]

If this is only a 60 liter (16 gallon) tank, there are way too9 many fish, and most of them are potentially too large for this tank. Sorry, but you have got to remove some of these or they are not going to make it.

Obviously the guy in the shop is clueless about fish and tank sizes if he has suggested/approved all of these fish. This tank is too small for mollies (they grow to 4 [male] and 5-6 [female] inches), swordtail (they attain 4-5 inches), angelfish (6 inch body length with a vertical fin span of 8 inches), Conge Tetra (attain 3-4 inches and must have a group of six-plus). Will the store take these back? They should.

Now to explain a couple other things in answer to your questions/comments in post #5. First, shoaling fish. These fish "expect" to be in groups of hundreds of their own; this is programmed into their DNA. We absolutely cannot alter this is any way, it is something that must be provided.

Second, the "they seem fairly well..." is something you cannot possibly know unless you can somehow talk to the fish. We must assume the fish will be as it has been created through evolution, expecting this and that, and functioning best in the proper environment. Almost anything that is at all contrary to what a fish species is designed for will cause stress, this we do have scientific data to prove beyond doubt. The fish's homeostasis, the internal system that keeps it healthy and alive, only functions well in a very specific environment. And "environment" means the water parameters (GH, KH, pH, temperature), the aquascape, tank size (sufficient for the fish to "live"), numbers for shoaling species, tank companions (not all fish can live together because of all of this), water current, light...there is much to consider. As soon as any of this is not what the fish was designed for, it will have stress. Fish can be under stress for quite a long time before showing it.

The only fish mentioned that will work in this tank are guppies and neon tetra. But this brings me to water parameters, which are not given. We/you need to know the GH and pH for your tap water. Neons will be healthiest in soft to moderately soft water, guppies moderately soft to moderately hard (or harder) water. Mollies (though too large for this tank) absolutely must have harder water or they will weaken rapidly.

Byron.