Tropical Fish Forum
Tropical Fish Keeping Help and Advice => General Fishkeeping advice => Topic started by: Etienne on July 31, 2013, 06:41:11 AM
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Hi all,
I have 6 harlequins, 6 cardinals tetras and 1 DG in a 60L tank.
The centre piece is the shoal of harlequins, they are always active, swim about and occupy the middle/top of the tank. The DG minds his own business swimming at the top most of the time.
The tetras are always split in 2 or 3 small groups near the bottom and only seem to be getting together at feeding time.
Here is the question: are they just trying to stay out of the harlequins way or the shoal is too small for them to feel confident?
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Are you asking if more cardinals would make them swim as a group, or if more of them would make them swim in all parts of the tank?
It is possible that more of them would make the cardinals swim all over. I have noticed that my related green neon tetras (Paracheirodon simulans) tend to keep to the back of the tank - except when they can't see me and then they swim all over. If I sit in the armchair and keep very still, they behave differently from when I stand in front of the tank. Do you watch your fish from close to the tank or from a distance? In other words, are your cardinals doing the same as my green neons? It could just be in the nature of Paracheirodons to hide if they see something large moving near them, in which case upping the numbers won't help. But you could try an extra two or three and see what happens. No more than that or you'll have too many fish.
But adding more won't make them swim as a group, if that's what you meant. Schooling (ie swimming as a tight group) is defensive behaviour and most shoaling fish only school when threatened. Some shoaling fish do school more than others, but cardinals are not among them.
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Hi Sue,
I was asking both questions at once: a shoal that would go up in the tank. I will look at the fish sitting quietly see if there is any change of behaviour.
I won't add any tetra as my tank is actually well balanced in terms of layers. If the tetra move up, the bottom will look bare. Could be also that with the harlequins running the middle of the tank they found a natural place at the bottom since I don't have any bottom feeder.
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It might well be Paracheirodons. Even when I'm watching from the chair, my green neons may come to the front but they are still in the bottom half of the tank. If you are happy with your fish layers I would leave them be.